guess it depends on what you define by violence/"running" around with guns/knives....
If someone is holding a gun/knife/sword, something like Kenshin posing or the Naruto characters in a defence/attack phase, it's not that bad. However, if there's unnecessary blood/gore all around, the character is smiling or smirking after the kill.....(eew!)
....that's really uncalled for.
I strive to eliminate any form of weapon/gun/sword/magic out from my drawings, and stick to good old normal mortals as characters.