From If This Isn’t From a Book, It Should Be:

One of the worst ways to stop someone from telling sexist jokes is to tell him the joke isn’t funny. He’ll assume that you’re humorless and that he needs to save the good stuff for the right audience. If you really want someone to stop telling sexist jokes, you need to tell him, “I don’t get it” and then step back as he tries not to say, “It’s funny because women are stupid.

Posted this to Facebook but it’s too good not to keep sharing. Discovered via Ashe.