It's an interesting little psychological study. I think what got Richards in trouble was that he mixed the racist thing up with what may have been a warranted reprimand against a heckler. "Is he leaving?" Richards says after the initial comments cause the man to walk out in an understandable rage. Richard's rage and indignation at being interrupted are evident, and the attempt to cloak them as an over-the-top racist diatribe was the worst possible choice he could have made.
What's more, I think you can see a change in Richard's ironic slinging of racist terms, to what becomes some real verbal crossfire by the end of the performance. As Ebbie said, "that's what you get for interrupting a white man!" is a statement which, when put beside "well you interrupted me pal!" as a justification, implies that the sentiment is more than just ironic.