Well if he's like that he obviously doesn't deserve to have you as a friend. It's incredibly mean of him to speak about you and he certainly doesn't have the right to do just because he's ill.. However i still don't think you should give up on him, especially while he's going through his illness. I think you should be the better person and forgive him, at least until the whole illness thing is over. I'm sure he needs you even if he pretends he doesn't. Maybe he hasn't been particularly nice in the past but maybe he's over doing it now because of stress or because he's emotional or whatever at the moment. But regardless, i don't think you should give up someone in a time of need because i'm sure he needs someone by his side atm.
Just an opinion..