There are a large number of people who are alive right now who would be dead if Nelson Mandela did not exist. If you disagree, you can feel free to look at how well Zimbabwe’s done and wonder if he can’t be a lot of the difference.
Mandela is not an anti-Zionist in the sense I think you mean it (meaning someone opposed to the continued existence of the current state of Israel in its form as a Jewish State, as opposed to someone who is not in favor the concept of a Jewish homeland or is broadly sympathetic to the Arab population between the Jordan and the Mediterranean), let alone an anti-Semite. (Again compare the trajectory of the Jewish population of South Africa to that of Rhodesia/Zimbabwe, it’s not close.) There’s no possible justification for putting a YMS after his name.