I'm kind of torn about Mangino. I work in the stone industry and one of our sources for limestone is in Kansas, I asked my contact about this and it turns out his son played on special teams for a couple of years there under Mangino. From what he tells me it wasn't a matter of one or two incidents of comments or trying to be a strict disciplinarian. Some of the comments were very personal in nature and insulting, certainly beyond the scope of motivation. It sounds like players finally started to compare notes and realized a pattern.
Some coaches are notorious for comments like these and use them for motivation for players, most of those coaches make sure to seek those players out after practice and inquire about them, any issues they may be having etc, basically just building a relationship with these kids and letting them know they care at least on some level. It appears this was not the coaching style of Mangino. It appears that after a while the opinion of the players became that Mangino was just a mean spirited guy, they believed his actions more closely resembled bullying than anything else, certainly not constructive in the players views anyway.
I'm not saying whether these players are right or wrong, just trying to give insight as to what people inside the program believe. Part of me believes that many of these players probably let Mangino get to them and took it personally. The other part believes that Mangino has a particular style of handling his players that some people are not going to react to well. There has been a lot of talk about Mangino perhaps having some problem with self loathing and projecting that outwards on his football team and from what I gathered from my contact I think he believes this to be the case.
Take this for what it's worth. I personally believe Kansas will not do any better as far as a guy that can get it done on the field, but it was obvious the situation had turned a little too toxic at Kansas for him to stay, at least from the universities perspective.