It's a quality issue. Baseball was almost killed in 1919 by the Black Sox, and fortunately for the game, that the next year Babe Ruth really became baseball's biggest star and saved the game.
I know Rose didn't bet against his team or tank games, but it's the threat of someone else doing it that is the problem. If you let Rose get away with it, you have to let anyone else get away with it to.
At the same time, if Rose has anything in his corner, it's the fact that he didn't bet against his team or do anything to tank games.