Check out some gameplay footage and judge by yourself! Other than the cussing, I think it’s pretty tame compared to more disturbing games out there ( See Outlast ) with much more taboo violence. This one is just good ol’ fighting violence, not a psychologically-scarring type of violence ( again, unlike Outlast ).
Just explain to your son that pounding at people and pretending to be a monster isn’t right and that it should stay in-game, and make sure he understands that.
( And like others said, don’t allow Mic, or just let him play offline-- chances are, he won’t even realise he’s playing against AI. )