Kelly haters break down into 3 categories:
1. The ignorant. They look at the manufactured narrative of him being a "yeller" and "mean"... all from the one game against USF 3 years ago. He's not even in the top 20 of most animated/yelling coaches, but none of these other coaches ever get called out on their stuff, and they aren't on national TV half as much as Kelly. Ignorance sometimes extends to Sullivan/Seeberg/Kekua but that's pretty rare... usually this crowd just "doesn't like him" the same way ignorant voters just "don't like" a certain candidate while knowing nothing about their platform.
2. The self-righteous ND hater. This group of anti-ND people try to stretch everything they can to be laid at Kelly's feet. He's a "liar" because he left Cincinnati... you know, after being man enough to tell all his players face to face unlike many other coaches (Franklin, Petrino, etc.)... you compare Franklin's exit to Kelly's and it's just hilarious the contrast. He also "covered up rape" and "killed a kid"... it's so important for these morons to justify their hatred for ND and make Brian Kelly a devil-like figure that everything is turned into the most fitting derogatory hyperbole they can that serves their end.
3. The legitimate Kelly hater. This is by far the smallest group and is generally comprised of people from southwest Ohio. There are also a small quantity of people (like the old Crete-Monee coach) who disliked Kelly from prior events. This is the only group of people where it's even understandable that they don't like Kelly.
As a very relevant aside, there are virtually no legitimate people in the industry who dislike or don't respect Kelly. This is in stark contrast to Willingham (not respected at all) and Weis (incredibly disliked by many). It should tell you a lot that the most informed people raise zero legitimate gripes with the man.
lest we forget the ND fans who are not big fans of Kelly...they're out there!