I think it's generally a rule of thumb not to heckle a comedian, even if they suck. I mean, even the worst ones work hard at what they do, and don't deserve the comments.
On the other hand, most decent comedians know what to do when they're being heckled, and that can lead to some of the more entertaining stuff of the night. As a matter of fact, I've been to more than one stand-up concert where it appeared to me that a "heckler" was actually a plant the comic used for precisely that purpose.
Well, when you go to see Gallagher, you expect one liners, oversized props, and of course, smashing of items. (or if you come to his more recent shows, the material is significantly more over the edge) When he totally throws that away and rails at a heckler for a lengthy period of time, that for me would be money down the drain.
Only once did Gallagher do an entire act without props... on The Tonight Show Starring Johnny Carson. Johnny was not a fan of prop comics, so Gallagher had to pull his clean jokes (some which were George Carlin's old jokes) and rely on them.
I am a stand up comic myself, and I've never known anyone to plant a heckler in the audience. The only professional I know that did this was Andy Kaufman. His agent/writer Bob Zmuda would heckle either Andy or his (at one time) alter ego Tony Clifton. In Zmuda's book, he says he heckled Andy while he was doing his foreign man/Elvis act. This was only a year before Andy's death, and Andy was losing his hair, and started using an Elvis wig. Without telling Andy, he went ahead and pointed out that Andy couldn't use his own hair to do Elvis anymore.
To point this back to game shows, Andy Kaufman did appear on HS. According to Peter Marshall in his book, Andy was giving the producers a hard time by being in character and being impossible. He eventually snapped out of it and talked to them as himself.
