I think there is also something about using the word "ban" in this context. I haven't "banned" guns in the house, I just don't buy them, and know that they wouldn't be given one. My ds has occasionally, when asked what present he would like in a shop asked about getting a gun, and I have just said "no, what about this toy instead". It's never been a problem, so I can't see why he should suddenly develop a huge desire to have a real gun as a grown up.
Most children (girls and boys) have no problems in expressing their violence without firearms, whether they use bits of toast, fingers, sticks or anything else that fires their imagination. I don't see that he is being deprived in any way of any part of his growing up.
I would have no problem with him taking up fencing as a sport, and we are currently looking at a karate class for him (recommended by his physio).
I like many others here, just do not like to see children (or grown ups for that matter) with anything that looks like a real gun (or knife or anything else designed to cause pain in others).
That doesn't mean I have a problem with other families having other views, and would not be upset if he played with a gun in a friends house (so long as I don't have to watch!).