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.