It is a shame you edited your post. It doesn’t remove your mistake. (But makes it hard to make sense of the posts pointing to it!) Do you agree that you made a racist assumption about the sociologist, discarding his words on the assumption that that he was white? Perhaps you have also made a racist assumption of the worth of the other sociologist’s work based on his colour?
The lecturer may well be racist by your definition, but you are also revealed as racist by your error.