I always tell my students that they are here to learn and I am here to teach; and if we have personalities that conflict, then we should not lose focus on our goals. Personality conflicts (teacher/student or student/student) are absolutely devastating. It can shut down the class. We address these problems immediately. The fallout from a conflict between two students can affect 50 other students. Most of them will tolerate the situation, but none of them like it. Our teachers are counseled that a happy class will have a lower attrition rate than an unhappy one. I can't see the fault in that logic.