I'm not going to go against science and say that testosterone has nothing to do with aggressive behavior, of course it does. It's hardly the sole factor in aggressive behavior though. Men with high levels of it aren't destined to act aggressively, nor are females with very low levels of it immune to aggressive tendencies. It could be the reason why we see more violent and aggressive behavior in men rather than women, OR it could be that women are aggressive in different ways.
In any psychology class they will tell you there are two types of aggression, physical and relational. When only considering physical aggression men are far more frequent, but when factoring in relational aggression it's basically the same. So there may be no actual difference in aggressive tenancies at all between genders, just how each expresses them.
Whatever the reasoning or pattern is though, it doesn't take away from the fact that just because someone is male or female, that they will act a certain way in a certain situation by virtue of what they were born with between their legs. You can't blanket a whole group of people as such. It's okay to keep generalizations in mind of course, but applying them to every member of a group you shouldn't, I think.