Well there are idiots out there who will be punching the shit out of a digital cop and think it's really fun and then proceed outside to punch a real cop. I'm sure that shit would happen, just as it does now when people jump out of a 27 story window because they died in World of Warcraft.
Just because some idiots can't handle a certain something doesn't mean it should be illegal for the rest of us. That's like banning stairs because people in wheelchairs can't use them (god, how many times have I brought that one up in these discussions
).