1. Mandela wasn't a dictator, much less an evil one. He was a one-term president (voluntarily served only one term so as to not follow in the footsteps of other African leaders) who could have done a lot to make white life hell if such was his intent.
2. Of course he engaged in violence. What kind of weakness must be infecting your mind to think that violence was not a justifiable response to Apartheid?
The man was far from perfect, but considering what the preceding forty-odd years looked like, he was about the best we could hope for as far as a black leader goes. He largely (even if just publicly, for political reasons) left his hatred in the past, and even if he still harboured racist sentiment, he didn't let it show.
You'd be hard-pressed to find a South African of any colour who isn't at least a little bit racist (we recently had a member of the opposition party go onto Facebook and make a comment about all the monkeys on the beach, for instance) and you don't have to look farther than our current president to find the sort of asshole who would have turned this country into a tyrannical bloodbath after the dissolution of Apartheid.
I often wonder how a guy like
@SouthoftheAndes (who has preached that making peace with evil dictators is against Western values) would recommend people resist a system like Apartheid if he were a part of the group oppressed by it.