Best way to deal with them is to not performYou are not better than them by making smart comments, or trying to make them look foolish, you are just as bad as them. They are trying to make you look bad, so you make them look bad? How does that make sense? If people aren't going to appreciate your magic, don't perform. If it spoils it for others, then they will hate the Heckler for ruining it for them then the Heckler will go cry in a corner and everyone wins. Hell yeah.
This is so true... I mean, why try to impress someone who obviously isn't interested in what you're doing. And if it's a group of people, either they'll get the heckler to shut up or they'll be let down and be mad at said heckler for awhile.