This is a really interesting question, and though I may not have a straightforward answer, I do have some thoughts...

First, I don't necessarily think it's a bad thing to approach something unfamiliar with caution and suspicion. It's natural to want to protect yourself before fully understanding how something works or what its purpose is. We do this in all facets of life, relationships in particular (keeping that wall up until someone has earned our trust). It's dangerous to welcome something completely unknown with welcome arms without understanding its potential, purpose or capacity.

That said, I don't think that we can make a generalized statement for how each part of the world would treat these alien beings. Disparities in scientific and religious beliefs already divide our world and lead to vast differences in behavior. For example, I can see the scientists of the world welcoming them with open arms, and being inquisitive, friendly, approachable. But, I can see religious extremists meeting these aliens with much skepticism and fear - perhaps protesting, maybe even waging a full-on "holy war".

What I think is the MOST likely outcome of an alien visit to our planet is this... one or more countries see the potential to leverage them as an advantage in battle with another country/countries. If these aliens have the ability to transport themselves through space to our planet, they hold immense ability to help Pakistan obliterate the United States, for example. I can see alien lifeforms being used to significantly alter the existing landscape of the global community - to effect power shifts and move forward pre-existing wars / tensions between countries.

Sadly, I just think that ultimately, mankind is abominably selfish and would only be able to see the "good" in alien life if it would somehow advance man's current plights.

The most important part of this answer, I believe, is that almost all of our science fiction movies grossly underestimate the technology the aliens will certainly have. I think this simply reflects our limited human imagination, but believing that aliens with the technology to travel a bajillion kilometers across the galaxy will suddenly have engine trouble after they get here or fly around with their running lights on or clumsily get caught by humans is naive. They will be so far advanced that it'll be like human scientists observing wildlife in Africa: we really won't know what to think about them at all.

That said, yes, studying wildlife in Africa can be a dangerous business and sometimes people are injured or even killed. It's not like we'll be any sort of threat to the aliens, but they will have to be careful. So, ultimately, it won't matter to them at all whether we welcome them or treat them with hostility any more than it matters whether the lions welcome the biologist or want to attack her in her SUV.

And if they are here as invaders, there really won't be much we can do about it as they systematically clear us out, maybe allowing us to continue on in protected areas or something. Did it matter whether the Native Americans welcomed the Europeans or were hostile?

From our end, of course we'll be hostile, which, yes, is sad. I mean, the freakin' Sunnis can't get along with the Shiites, the Protestants hate the Catholics, the Serbs want to kill the Croatians and the Tutsis almost wiped out the Hutus (to cite four examples). From an outside perspective, it's really hard to see any differences at all between either of those enemies-to-the-death pairs, so there's basically no hope we'd get along with aliens.

When you look at the reflection of emotion in Science Fiction movies pertaining to alien visitors, you almost always see a defensive fear on the humans part.
It doesn't matter if the alien visiting is a friend or foe, they are still greeted apprehensively.

When you look at film over the years, you can't help but notice that emotions, reactions or inflections always have a bit of truth to them.

Me personally? I would hesitantly be curious of an alien being until I was sure that this entity wouldn't harm me. But I can't speak for the world.

If the world still alienates and abuses others that are not like them, I don't see us being any nicer to a Martian. Sad but true.

The reception would be mixed. Some people would welcome them, some would want them killed. A lot of people would try to make money off of them. Then there would be anti-alien groups and consipricay nuts who think that the aliens were created by (Cheney or Obama) to scare the american people.

I do believe there is intelligent life out there and I have given this a lot of thought over the yeras as I have watched movie after movie about what our first encounter may look like and the differnet perspective from which each movie is made. Here's the conclusion I have come up with...

If there is intelligent life out there and they do come here and make their presence known, they are obviously much further advanced than we simply because they have figured out a way to travel across the galaxy to us. So, obviously they are technologically superior to us, right? I'm assuming this means they have probably been around longer than we have here in Earth. So, they are probably more highly evolved as a species than we are. They've been around longer. Their society is obviously more highly evolved than ours and this would point to the conclusion that they are peace loving. If you still aren't convinced they are peace loving, look at it this way. If they were going to annihilate us, they would have done it already.

The reason we here on Earth have some people who seem to always have their fingers precariously close to the fire button, is because of fear. I believe one day fear will be mostly bred out of us as we evolve, but for now we still have much fear and fear leads to violence. I believe this is why they haven't made contact yet, because they are actually scared of us.

Think of it like this...when you are observing a small wild animal in the woods (let's say a fox for the sake of an exampl), you don't want to bring it to the attention of that wild animal that you are there, right? Why? Because it may be rabid and come hurt you? You know for a fact that little fox can't kill you, but it may bite you and then you would have to go get shots and it would cost you money and time and effort. So, rather than take that chance, you sit back and observe. Now, take this example and apply it to the scenario of us being the fox and they being the person walking in the woods.

Now, with regards to your question about us being civil with them when they do make contact, I really don't think anyone would be ignorant enough to ridicule them because they are differnet. They are obviously way more technologically advanced than we are. To ridicule them or discriminate against them would be like a some average person making fun of some super hero (let's just say they exist for hypothetical purposes). Now, what kind of idiot would spit in the face of Superman? So, no, I don't think discrimination against them would be a problem, but if someone was stupid enough to do so, I believe they are highly evolved enough to understand why the person is being so ignorant and would simply pat that person on their proverbial head and move on without a second thought to the idea, realizing that person just isn't as highly evolved as they are and that life is a process, not a product and we are all evolving to the best of our ability.

There are 3 probabilities.

The First :
The alien will come to our earth in peace
Second :
They will be invaded by us
Third :
If they are looking for meaningful material(s) but we resist, they might invade or steal something from us stealthily.

It's about us how to behave,

* The reason of the first statement why I told the alien will come to our earth in peace is because of the high-tech science that they have.
- Why would I say that they are high-tech science?
It's because if they have succeed passing our atmosphere and the air in the earth, they must have been learned it, so they can come to our earth safely.
- Why would I say that alien will come in peace?
It's because the more civilized civilization, they won't try to war, but they will find something interesting in our civilization. maybe it is our materials in the earth, etc.

*The second reason of the statement why I told they will be invaded by us (human) is because we have a bad feeling about alien. It's because most of our media that told us that alien is a cruel creature. It's reflected on the "war of the worlds" radio broadcasting that makes a mass panic everywhere.
otherwise, we will start thinking about our home, the earth. As the owner of the world, we become suspicious about their presence. It can lead us to intimidate them and at the end trying to kill or drive them out.
-Why would I say that we'll try to kill them or drive them out (and maybe they will also attack us)
It's because we feel anxious about the technology that they have so they can land to the earth safely, I'm sure we have a suspicious mind about their arrival. Just like in the communication science, because of the insecurity, we might think about the massacre, genocide, etc. but, hopefully, if they are highly intelligence creature, they can understand us and trying to solve our misconception.

*The third, Why I said they will invade us if we resist to give them what they want? it's because of the thing(s) that they're really want to improve their home's technology. What we are really need is cooperate with them, it isn't hard to do. Just make a trade route between two of us.
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I'm sure as a civilized creature (alien, because if they pass the atmosphere and can breath in this world they must be a intelligent creature) they wont attack us but trying to share us their knowledge. And in return they may try to find out and learn our cultures and maybe trying to get some materials.

The conclusion of this case that the alien wont try to attack us, but sharing what we have and what they have.

Something tells me that if aliens came down to Earth, we would behave just like in the movie Mars Attacks!
slightly slow at first, causing our own dismay even if their intentions are friendly, but ultimately engaging in a disastrous fight with them.
Unlike in the movie, I have a feeling that a lucky fluke would not save us this time :(