1. There are plenty of people who don't know of Mandela's terrorism, nor his communist connections. Its helpful to post links so folks can inform themselves. Just making a flat statement without support may make you a target for those with a predisposition to lionize. Kinda like if I just say Abe Lincoln was a tyrant and did huge damage to this country. While true, unless I support it with links or at least facts, its just gonna annoy even decent people.
2. You don't have to reach Mandela's terrorism or communism. All you have to do is point out the ridiculous contradiction that he supposedly worked for freedom, but then presided over a government that ruled others without their express consent. Doesn't matter much whether he accomplished anything for freedom if he became a government president.