The answer depends on what definition of "hero" she is using. The definition that reflects common usage is "a man distinguished by exceptional courage and nobility and strength". If we consider Joseph Stack's actions, it is difficult to see nobility in an action that would be expected to kill innocent people, and which indeed killed one innocent person. Ms. Bell's later statements saying her father's actions were "inappropriate" and "wrong" show that had she been using this definition of "hero" she would be contradicting herself.

A different, and less commonly used, definition of "hero" is "champion: someone who fights for a cause". Had Ms. Bell been using this definition, one could see how she might plausibly call her father a hero, though an obviously misguided one. He indeed was fighting for a cause - the abolition of the IRS. However, even when one fights for a cause, one has to take care not to hurt innocents (the end does not justify the means). In this, Stack obviously fails the test, hence even if one was to call him a hero, one would need to amend and call him a misguided hero.

In the final analysis, as most people understand the term "hero", Joseph Stack was anything but one. Stating that his actions were "misguided" is an understatement of rather epic proportions. Considering the source however, it is very human for the child of such a parent to try and find some merit in her father, even where most would fail to find such.