It is not in fact generally the accepted standard among professional comedians than it's legitimate to attempt to be funny "about anything" so long as you have a decent chance of getting a laugh.
I've seen professional comedians joke about the holocaust, war, abortions, slavery, cancer, kids dying, pedofillia, incest, serial killers, 9/11, torture, religion, and lots of other things besides.
Sure it can. One joke was about how there was a video of the vegas shooting, and there was a guy running out of the frame with a full beer, as if shielding the beer was the most important thing in that situation. "The beer must've been pretty expensive... But the shots were free."
It's tasteless, yeah. But it's comedy. It's hard to say there are limits.
I think that bit was awesome. Norm MacDonald is a great comedian, and he can deliver everything just perfectly.
That's a perfect example of a comedian taking something supposedly solemn and turning it funny. Kind of like when a chef takes an off-cut of meat and turns it into something delicious.
I'm utterly confident that if I looked I could find examples of comedians telling jokes about those subjects and audiences laughing.
For example, I just searched Google for "comedian pedophilia joke" and the first result is about Louis C.K. doing one during an SNL monologue.
Nothing is off limits in comedy. Plenty of stuff is in bad taste, but as long as the comedian is actually trying to be funny I think most or at least many other comedians will back them up.
There's a long-running Holocaust denial joke in most episodes of Norm Macdonald Live that's hilarious. You're just not watching enough comedy if you don't think anyone makes Holocaust jokes.
Everyone downvoting this doesn't understand comedy. So some comedians make (for example) Holocaust jokes. They are careful about doing it in a way that doesn't disparage Jews, even though it might be shocking, off-the-cuff sounding, &c. Professional comedians can do this because they're experts at telling carefully crafted and targeted jokes in a way that sounds natural. It might be very shocking, but not shocking in a way that fosters racist feelings in the audience.
If a comedian showed up to a mic and started making the sort of Holocaust joke that an insensitive person would make after a few beers, they might get some laughs, but laughs aren't the goal--the goal is to have a good set that people like and remember. Their set would likely flop and they would likely not invited back. I dabble a bit in comedy and, yes, I have seen this happen.
This example holds for most sensitive subjects. So no, it is not acceptable in comedy to say anything for the sake of getting a laugh.
His point is that you're allowed to try to be funny about anything, and if you bomb, you pick yourself up and dust yourself off. You should be allowed to make the attempt.
I will agree that the more sensitive a topic is, the funnier you gotta be. The joke should have an insight and good timing and delivery and all that. If you're just saying shocking things for the sake of saying shocking things to try to elicit a reaction, sure, you won't get asked back.
However, that shouldn't be a reflection on how sacred the topic is, but how unfunny you are.