A great comedian can take a tough social issue and break it down into something that people can laugh about. Whether it's race, sexuality or good old fashioned religion, with a solid set-up and an effective punchline, jokes can cut to the quick of issues that other forms of conversation can't.
But one side effect of the art form is that sometimes the material just blows up in your face.
Here are fifteen examples of comedians who not only tread the line of appropriateness, but blew right on through and crossed it.
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