Would you make the same argument about a war film? Violence is a necessity there, but it doesn't mean people want to commit or see real violence, or be in a war.

Also, you could just as easily transpose it to something tame in reality. Kids like to put on capes and swing sticks around like swords, not because they want to kill stuff, but because it's fun to play pretend. Turns out grown ups like to do this too, we just call it cosplay and video games.

I think that games with optional violence are more contentious. If violence is the only way, you are putting yourself in soldier mindset pretty quicky. You kill to defend yourself or your objectives. And this makes everything ok because our culture sucks and if you have to kill because that's the rules, suddenly everything is ok and you are absolved.