C.H.
First if you think that only boys can be aggressive, then you need to get a different perspective. I don't think guns are bad or that they cause Aggression. I believe in properly educating everyone on the proper usage of firearms. I have 4 boys and believe me, they didn't know what guns were for awhile, and they are plenty aggressive, but no more than my sister and I were. My sons have learned what real guns can do and they respect them.
They don't always play Cops and Robbers or Cowboys and Indians. More like Autobots and decepticons. They have a lot of energy, but they still know the boundaries.
But if you are going to go around with the attitude that the GUN is the problem, just throw it away and duck you head in the sand.