He must have been VERY unpopular in high school.
There are enough people in the world to provide examples of how to learn from an unpopular youth, that Moore might have learned from them and taken the high road and acquired some social and reasoning skills. Unfortunately, there are also many who let their childhood turn them into exceedingly unpleasant adults, which seems the route that Moore took.
The factual errors, bad reasoning, and absence of perspicuity in his films demonstrate little desire if any, to inform. They seem driven by bitterness, and indulging the bitterness is a more plausible explanation of their content than any determination to inform the public. In general I don't think it's a good policy to psychoanalyze writers and filmmakers, but Moore's output is so uniquely hateful that it begs to be deconstructed. It's far worse even than the commentary of TV pundits like Olbermann and Limbaugh, Maher and Coulter, Huffington and O'Reilly.