Yeah I believe that's what started it, but I think what rubs people the wrong way is that here is this guy that (as you say) is bluntly honest — to the point of being rude — to people. Yet when people are bluntly honest with him, he reacts very negatively.

Edit: You say "bullying," but I would suggest that he maintains his online persona in such a way as to generate controversy. He comes off as very abrasive, even annoying, at times. I felt that he specifically tries to spur such reactions with his comments.