Well, the joke is a play on those gender stereotypes, the blonde waitress clearly knows much more then even the optimistic mathematician expects. The butt of the joke here is the university system and the jobs market.

That's true, but frankly, would you tell this joke during a conference? Personally, I'd prefer not to, even if it was relevant.

Seems very unlikely? This joke is obviously punching up instead of punching down. Feel like a lot of people worried about cancel culture have some kind of bogeyman in their head that doesn't reflect reality at all.

Even if that wasn't the case: the niche nature of the joke protects you against global outrage

I wish it was a bogeyman. The Donglegate happened because someone overheard a joke between two friends. Then people have been fired. I'm very, very careful about every joke I tell and who is around.

Did you stop reading then? Because the actual joke is that even the guy that thought the average person numerate stereotyped her as dumb and was wrong.

An absurd example of a 'blonde joke' to object to if you're going to.

That's my very point: there are people who will find it offensive neverheless.

The joke is an explicit rejection of that particular trope, though.

I think the idea is that the one who would feel offended by this joke, could also only see the trope and not the fact it was rejected. And if you dare to explain it, you automagically end up in a deadlock.

It also unlocks the tactic “I will play dumb for a while so you don’t feel too smart anymore”. If you want to continue to do good, don’t open up for stupid attacks — politics 101.

You didn't understand the joke did you?

Agreed. Although it should be fine if you know your audience and redact only as needed.