I guess it's because our own worst nature is to tear down others because of their imperfections.I guess you do the so-called "body of work" review and if on balance more positive than negative then okay. However in that review egregious conduct weighs in more heavily.
Knight did not win at all costs, did not pay players, did not pressure teachers to pass failing student athletes, did not violate ncaa rules.
In the end he had this horrific temper and little patience for dealing with media. He taught basketball as well as anyone ever, he prepared teams as well as anyone, ever. He possesed more integrity than most men we honor.
You wish that you can separate out negative characteristics and leave the good. We are all imperfect, but our mistakes and worst failures - at work, in our relationships, don't get played out in the public eye.