A coach can be any combination of sleazy, upstanding, likeable and unlikeable and everything in between. If we look at those post WWII with multiple national championships, it looks pretty close between those who were sleazier than average or jackasses or both and those who were neither. From what little I know, Saban, Bryant, Hayes, Meyer, Osborne and Switzer were one or both and Royal, Leahy, McKay and Wilkinson were neither.
Of our best coaches, I'd say Neyland, Majors and Heupel were or are neither but of course that's subjective.