A sportswriter (I think it was on CNNSI.com) wrote an article a few weeks ago about Artest. He said that Artest was actually a really likable guy, but was just flat out dumb.
On the most superficial of levels, Artest was not dislikeable. He wasn't a glaring, angry person giving off violent vibes. But it's hard to like someone who commits violent acts and then refuses to take any responsibility for them. He is not merely dumb, though he is surely that. He is morally obtuse and, ultimately, dangerous.