Agressive?

[Angrboda]

I think your OP is conflating two separate senses of the term aggressive. One is to be more than assertive in attempting to establish one's presence and command of an environment. The other has to do with anger, hatred, a tendency towards violence, and "seeing red." I think it's the aggression in this latter sense which I think most theists are picking on. Whether it's a valid complaint or just a self-serving distortion is another matter. It's a part of Western culture, inherited from Plato and Augustine on down that strong emotions are a part of "the bad part of ourselves," of the body rather than the spirit, and so western ethics emphasizes emotional tepidity and self-control. From that background, anything smelling of strong emotions is immediately suspect, and even, perhaps, a symptom of a character flaw (or a mental illness). I haven't thought it through a lot, but I see atheist aggression as primarily an expression of righteous anger, of caring about people and the world enough to not let it be fucked over by belief in irrational fairy tales. There's also the element that, historically, even presently, the religious are guilty of a lot of evil and oppression at the behest of their beliefs, so there are very real things to be angry about.

I can't say I've sufficiently thought through the whole matter, but I don't see atheist aggression as in itself a bad thing (assuming it exists). I guess that raises two questions. Why do theists think the specific aggression of atheists is a bad thing? And, independent of what theists think, is it in fact a symptom of a problem. (ETA: It also occurs to me that anger is often a reaction to misunderstanding and strong differences of opinion. Because of both the differences themselves, and because things like cognitive dissonance encourage us to ascribe lying, delusion, or stupidity to those we disagree with, anger becomes a natural result. Same thing with Republicans and Democrats, alternative medicine and traditional medicine, Justin Bieber fans and everybody else....)

You might want to watch the Greta Christina video I recently posted, "Why Are You Atheists So Angry?" It's 45 minutes, but it's very good.

https://www.youtube.com/watch?v=GUI_ML1qkQE