The "right to heckle" is not the issue here, nor is the right of a comedy club to remove an unruly patron. What is being discussed is the injection of race into the heckling by an audience member of a comic. If this discussion was about whether Kramer should have stopped his show and asked for the heckler to be removed, then those would all be points to discuss. For this discussion, though, they are irrelevant and indicative of a mindset by you to find a way to excuse racist behavior, or nitpick the critics of it.
There is an old tradition of comedians to go for the jugular when dealing with rude patrons. Some will even prod the audience with attacks (like Don Rickles and Rudy Ray Moore).
Doesn't mean what he was saying was either funny or appropriate. But where do you draw that line? If he had called a noisy woman a "b*t*h" would it have made headlines?
It is really pathetic that some here are bringing up all manner of other situations in an attempt to dismiss the idea that what Richards said was bad.
Freedom of speech, double standards, heckler's statements, etc.; it boils down to Richards being a racist ass who doesn't deserve defending.