It's not hate. My own opinion is that TO was a great coach but a very poor administrator, and he's actually a big reason why the program slid into mediocrity.
He basically forced NU to hire Solich. He hired Pelini (which at the time was a very popular choice, so can't fault him for that one), and he along with Harvey Pearlman, orchestrated Nebraska's exit from the Big 12, which again, was popular at the time, but as we see hasn't been a good fit. Though I'm sure the administration loves the $$$.
I don't think the vitriol is warranted, but I do agree he's dragged the program down.