You know, people will say any old shit is good if they want to believe it. I was recently at a gig with very little merit. An eclectic collection of ill-fitting, often ill-conceived, junk. There were people messing around, or doing stuff that was simply self-absorbed nonsense (don't worry, I'm fairly aware that what I do on stage comes within the boundaries of that description too). An audience sat through this shit and politely, sometimes even enthusiastically applauded. Those people will have gone home trying to tell themselves that they didn't waste their time or ticket money and that there was gold within them hills.
It's this mass hysteria which I can use to whip certain crowds up into a frenzy. The majority of people in a comedy audience don't know enough about comedy to know whether I'm any good. If I appear to be enthusiastic and appear to be confident, then they'll often come along from the ride. If some other people in the audience get a bit too excited, the whole audience assumes that what I'm doing must be, itself, worthy of excitement and they jump on the bandwagon. As a result, I can sometimes do a lot better than an act of my ilk deserves... group delusion works a treat.