nooka, I suppose you'll just have to see how you feel when your sons are older. I thought it would be difficult for a child to play with toy guns in a non violent way until my ds2 proved me wrong. He showed me he could play well with other children and toy weapons.
I remember making more of a link between guns and misbehaving with my oldest son. If toy guns, and especially swords, were involved in a playfighting game, things were more likely to turn physical. But it wasn't a simple case of cause and effect as the hitting, tripping over, shoving around, bumping into each other etc could happen very easily when toy weapons were not involved.
tatt, not washing and stealing toys are more behaviour than taste issues, I think? Unless the toy stealing is because your son prefers his sister's toys, in which case it would be a taste issue too?
I hate boxing and wrestling, but did allow my sons to watch it on TV sometimes. However, now it is banned. It definitely made my sons playfight more and not stop when told to. Also as there is a 5 year size difference, copying the wrestling moves could have very dangerous.
So we had two big reasons to ban it - behavour and safety.
One thing to add (might have been mentioned already) - violent video games obviously have age recommendations on them. Adults often play the same games as children. So there is a good reason to say many violent video games are not appropriate for a 9 year old.
But as a rule, adults don't play with toy guns. The recommended age for most toy guns is 3 years and over. So as a toy for a child, they are age appropriate. Not talking of air pistols here, of course!