How honest do you feel a comedian's act should be? Have you ever found yourself unable to enjoy someone's set because you knew they were lying? Not something that was an obvious exaggeration or a goofy statement but something that appeared to be the truth, such as claiming to be single when they're actually in a relationship (or vice versa).
I'm fine with lying on punchlines. Going somewhere ridiculous is kinda the point there.
And little white lies are ok too. Like "I saw a crazy thing today" when it was actually weeks ago. Always surprises me how that can actually make a difference in a joke too. Immediacy helps.
But I dislike when premises are big lies. If you pretend that someone did something crazy and then you make fun of that fictional act, it just seems hollow to me. Or you make up a silly "this guy said to me" line and then mock it...well, what's the point? There's no there there.
The worst of all is when a premise is just clearly false. Like clearly that NEVER happened. Totally takes me out of it. When that happens, I can't even pay attention to the rest of the joke. It's like watching someone try to dance with a dead horse.
That's for me and my jokes and my p.o.v. If you're an absurdist comic or going for something else, making shit up is fine. For example, almost all of Steve Martin or Zach Galafianakis' act was/is made up of lies. And that's why they're funny. Different recipe for a different cake.