Everything else points to him being a stand up guy and he's one of millions of basketball players to have never committed a foul in their own mind. Just check out any ward ball or the RB. Duncan is a great guy and I guess if this is all people can point to to dislike him I guess that's a pretty good legacy.
By the way, I've followed him since Wake Forest and I remember in his first or second year in the league the coaches asked him to beg for fouls. They said you are a Superstar, act like it. Jordan and Bird were always playing the refs, so it's just part of gamesmanship on Duncan's part.