The comic's sense of empathy must be different from the writer of drama. Humor, and particularly satire, get most of its impact from a lack of sensitivity. Writers (and comics) get a high percentage of their laughs from direct or indirect insult. Sometimes the audience itself is the target of ridicule. How is this possible?
The writer and the reader (or comic and audience) form a pact with each other. The writer/comic vows to be funny, yes, but implicit in that vow is a shared humanity that makes it okay to laugh at someone, or at one's own self. The writer/comic can insult everyone in the audience, but once it become cruel or mean, people stop laughing. Why? Because when the work has too much spite and malice, the material generates far more tension that it releases.
Don Rickles is a master of the comic insult. It's clear going to one of his shows that anyone can become his target. And that's the point. He doesn't pick on one type of person. He picks on everyone. We all laugh at ourselves and each other. No one is left out.
I read a fascinating article in the New Yorker a couple of years ago about a group of therapists who discovered that schizophrenics who didn't respond to personal interaction came out of their shells when watching Larry David's character in Curb Your Enthusiasm. Why? Because the character reacts to life in a way that they feel true for themselves, that they empathize with. "Boy, I do that all the time!" A common comment watching one of this shows. The character in this show is venal, self-centered, lacks empathy himself, and he's always getting into trouble because of these same qualities. People (not just schizophrenics, me too) laugh at the show because it reveals the worst in us in a way that we can empathize with and laugh at, releasing our tension. "Hey, Larry does it, he's even worse than I am, maybe I'm not so bad."
And I think being insulted by Don Rickles may have been one of the greatest compliments of all.