From what I've seen, I think there is something of a chain reaction of self-loathing which begins at the highest ranks and filters downward to rank and file.
I've known people who are deeply self-loathing who then turn around and belittle, emotionally blackmail or insult to manipulate others into conformity. I suppose this could happen with people who are self-loathing and NOT JWs, but I absolutely think the group structure and stresses contribute heavily to the problem.
I think the "high" of being unique and special is ultimately outweighed by the "low" of not being unique or special enough to be worthy. Hence, self-loathing.