Let's face it Clinton, he blew it. There are lots of ways of staying one up on a heckler, most of which consist of being more experienced/heard it before/ don't give a damn etc. There may even be ways of racially abusing members of your audience in an amusing way although I can't imagine any however much I try. The bottom line is that if you are that upset by being interrupted in the middle of your precious routine, you shouldn't be on stage in the first place. Stick to TV if that's all you can do.