Why is it okay for A-Roid, but not Pete Rose?

Tell me this: Why is it alright for Alex Rodriguez to admit that he needed illegal steroids to match the excellence of other MLB players, but MLB is banning Pete Rose from baseball? Pete Rose [after his playing career] betted FOR his team. FOR it. He wasn't throwing games or anything. I don't get why A-Roid gets a big celebration for his six hundred, steroid-induced homers, but a player clearly deserving to be in the Hall of Fame can't even go into the Reds clubhouse. Opinions?