And in a class about neurology or developmental psychology, putting it to a question, "are boys smarter than girls?" and then using that to explore different kinds of intelligence, is a very different thing from a professor in an unrelated field declaring, "It's my opinion that girls are less intelligent than boys, blah blah, office hours at 3pm on Wednesdays, etc.."

One is ok, the other suggests a bias that's going to cut half the class off at the knees.