"Joking" is not an excuse for sexism

If we say derogatory comments are acceptable in the context of a joke, this basically allows anything, because anything can be construed as a joke post hoc. Suppose someone said: “Let me tell you about my trouble with blacks. Three things happen when they’re in the lab: (stereotype 1), (stereotype 2), (stereotype 3).” I think most educated people would regard this as unacceptable, even if the speaker subsequently argues that they were being ironic. However, substitute “girls” for “blacks” and for many people it becomes OK.