I'm not sure how I'd react if a user of something I'd developed came up to me and called it "the most white male fascist tool I’ve ever had the misfortune to use."

Dan Russell, one of the writers at Creating Passionate Users did the right thing when it happened to him. He took a deep breath and asked "And what made you feel this way?"

It may not be pleasant to deal with a customer who's all fired up about your product or service for the wrong reasons, but as the article Screaming Users Considered Good points out, you can learn a lot from users who are struggling with it, don't "get it" or have had a strong negative reaction to it.