I saw an interview with Rosanne once. It had to do with standup comedians and their act/trade, and dealing with hecklers.
The interviewer sequeyed into it by describing an event that happened with Rosanne, where a heckler said something to her telling her she looked and talked like a man, and Rosanne's response was "Well, you can suck my d!ck."
She commented that the heckler is apt to always make a fool out of himself, because the comedian has the mike, and can control the rest of the crowd. Therefore, as a heckler, you put yourself at her mercy.
It looks like though old Krammer lost control somehow. He wasn't going for the jugular...the impression I get from watching the video is he was completely unhinged.
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Kramer made a major mistake, one of the worst a comedian can make: he wasn't funny. Add to that he offended some of his audience, and he's now got less fans who are willing to spend money to see his act. I don't know what was going on in his mind, but what he did was both offensive and stupid.
Maybe in his personal life he's a sweet guy, I don't know. If I had to make a choice, I'd choose to avoid him.