I recommend the dialogue between Richard Witty and Aaron Levitt in this blogpost of mine from last night. Levitt says he was in Chabad for a number of years and observed racism in the group. I would like to add this: A couple years ago I did an article for which I met a number of Chabad people. I liked a lot of them, particularly a rabbi and his wife who had me into their home. They were so smart. The rabbi was a learned man and could tell you all about Christian Kabbalists and the appearance of Jesus Christ as prefigured in the Old Testament, numerologically. By the way, he was a convert. He loved Judaism.
The time I visited them in their home, they introduced me to their children and showed me their library and then we sat down in the living room to talk. The whole time there was a black maid there, in the kitchen, or taking care of the kids. Her name was Michelle. I only know that because at one point the rebbitzin said, "I'm going to take Michelle home now," and left the room and I saw the black maid and her standing there, then they left. The behavior could not have been aberrant. For them, anyway. It was too natural, and too glaring; this was a non-person as far as their important guest was concerned. I have no idea whether it is true of Chabadniks generally, though I must admit it has cast a shadow over the group for me. I did not publish the incident in the article I wrote.