There's just one flaw with that argument that's really rather obvious: Skeletor isn't interested in having a nice chat with He-Man 'cause he wants the Conan wannabe and his pals dead yesterday. The only words he wants to say to our boy is "Hey, He-Man!! MURDERED YOU!!!!" before divvying up Eternia with his imbecile minions. (Hint, he becomes the King of Everything while they'd be really lucky to get the warm steam off his pee.) While the Elly Pattersons of the world don't want to believe this, there is that sad fact that the world will never run the Hell out of nasty jerks who wanna stomp you into the pavement for shits and giggles and the sooner the tinies assimilate that fact and act accordingly, the better.
This leads us to the hidden flaw that really discredits the argument: the whole 'He-Man MAKES kids violent." This is bullcrap of the most foetid variety imaginable. Anyone who's ever sat down and watched a kid without blinders on can tell you right off that violence is part of the package. Kids don't need He-Man or GI Joe or Lion-O or all of the other action figure types with kung-fu grips to put the idea to smack someone they don't like over the head into their heads. What they need is mothers who talk to them about the cost of real violence and who leave the fake stuff alone.