I think Moviebob should probably be under government surveillance for some of the stuff he says. His political opinions make Mao look like a puppy dog. Shit at least Mao gave concrete if somewhat poorly reasoned explanations as to why he needed to kill people. Moviebob is just bloodthirsty. Would not be surprised if he shot up a steel mill or something one day.
Though if we're going from purely artistic stuff it's a close contest. On the one hand, Dobson is sort of a competent artist. When he tries he can draw. The issue is he doesn't try. Ever. And he flaunts not trying constantly and back when he had a mild fanbase he told them to not try either. So he was moderately competent enough to poison a bunch of kids, and then gave up forever. Moviebob's probably less offensive in this regard. His book is dumb and self-centered, and his movie reviews are boring, but he's never made a conscious effort to make more people do things the way he does them. Linkara's Lightbringer is legit Storytime of Pain tier material though. And he's all around a disgusting guy. If I had to pick between reading the Lightbringer or an equal amount of SYAC, I'd probably chose SYAC. So I think Linkara wins from a purely artistic standpoint. Or loses. Whatever.
Also I don't really get the hate for Doug Walker. He's not good, but he's rarely offensive. If anything I feel sorry for him. He wants to make real movies but he's both trapped by his persona/fanbase and clearly lacks the ability to make movies. At the very least he's not overtly malicious like the other three.