Overall, I think the teacher overreacted. To kick a student out is to give up on teaching that student. If he wanted to teach the student why he believes political correctness is important, he could've done so a lot better. Although he may not have had the time for that, and just wanted to move on with his lesson about web design or whatever it was for the sake of the other students, rather than derailing the topic that heavily for the sake of just one student.
I think the best way to handle it might have been not to respond to the student's question immediately, but to say, "we can discuss that during break if you want, but right now I need to continue my lesson for the rest of the class".