I will have to check (I think it is found in "Village Swaraj" but it may be "All Men are Brothers" which would make more sense thematically) but Ghandi specifically talks about his experiences in South Africa and how it finally opened his eyes towards his own prejudices.

He writes about the experience in Pietermaritzburg and how it took this experience to realize that all men are brothers and deserving of equality. This is not to say the guy was a saint, but to mention that I believe he came around.