Autoerotic asphyxiation can be a very dangerous fetish.

http://www.self-help-sexuality.com/autoerotic-asphyxiation.html

Firstly may I respectfully submit you may be a bit confused in your terminology because "FETISH" is a different thing to "FIXATION" and different to sexual deviancy or paraphilia, but you seem to be embracing them jointly as all the same?

A fetish is "an object" not an abstract thought. It is the object or objects that a particular person associates inside his or her own subconscience mind as having powerful aphrodisiac effects, which can be in arousing him or her to initiate sexual excitement exclusively in the mind of that individual or to trigger orgasm. It is more usually the starting gun to initialise a thought process which may ultimately result in orgasm. This can be within the framework of sexual intercourse with a partner or, in other cases, the commencement of a sexual fantasy alone with the orgasm happening by masturbation. This applies to both males and females and to both heterosexual and homosexual thought arousal, or it can be the trigger thought that causes the climax to end in sperm penetrating an ovum or else the ejaculation of the semen alone in the bed and hence most pleasurable moments of the fantasy just before its completion.

The point I feel you also need to consider further is that "a fetish" is not in most cases something you try out one day and swap for another one next day to see if that works better, but some pleasure seeking energy in your mind dating back to your psycho sexual development when you were very young. Nor is a fetish something that only "weirdos" have.in their minds when enjoying sex. The fact is we nearly all have fetishes throughout adulthood, which are most usually parts of the human body that habitually manifest themselves in our mind - most typically of course guys generally get sexually aroused by big breasts of a female, ladies often get aroused by specific parts of the male anatomy especially of course a big penis, but also often his hair, or his foot or sometimes his hand.

In no way can these thoughts be considered weird nor dangerous and the point is the fetish that causes the excitement and/or gratification is something that generally speaking remains fixed in the individual's mind often throughout their adult life and in some cases has to be involved in the erotic activity for the orgasm to be successfully achieved.

The two individuals participating together in sex will very rarely have the same fetish as one another but one or other will often co-operate to exploit the partner's fetish both to intensify the other's enjoyment and, if desired, to maximise the prospects of a conception being the end result perhaps when difficulty has previously been experienced in this occurring. So my answer to your question what is a dangerous fetish, would be some object that excites a person to have sex against the wishes of the other, such as a rape triggered by the perception of that factor which might not otherwise have happened.another dangerous fetish is when an adult male is sexually excited by the fetish of the bodily part of a child.

So when you ask about practices "being banned in the US", I am sure you are aware both rape and paedophilia are indeed serious criminal offences, and rightly so. Homosexuality is a serious criminal offence in certain countries outside the USA and can even mean the death penalty if caught in certain other countries, but these are not fetishes but fixations or deviancies.

I do understand that is not really what you are asking and think you really mean "weird fixations" that sexually excite, such as the fairly common excitement caused to some persons in being urinated on, or else flogged with a whip or cane or else the fists of another person causing blood to flow. These sorts of fixation or fetish can be dangerous only if the desire to create reality for maximum erotic arousal results in severe physical injury to the practitioner. I know of a case where this happened to a young adult in the British army who used to deliberately set out to enrage his barrack room mates in order to get the sexual excitement of being pounded by male fists, and his success in doing so led to injury and hospitalisation. This fetish with the male fist in conjunction with his own blood was clearly a very dangerous fetish.

But we are bordering here on fixations which are not fetishes. some people who are very masochistic, or have a very intense "Self Defeating Personality Disorder" do get secretly sexually aroused by their own humiliation and have such a powerful fixation to be seen to be severely punished, an experience leading to an extremely enjoyable orgasm for them during a subsequent masturbation, that they may confess to the police for committing some heinous crime they were really not involved in at all, just so that they get punished.That of course is "dangerous" for the person making the false confession, and also dangerous for society in perhaps enabling the real culprit to escape being caught and so still be at large while the person with the SDPO gets sentenced for a crime he or she never committed!