Jokes don't have to be false — it's actually in vogue these days for jokes to be accurate observations of reality stated in funny ways. For example, Louis CK's joke about the unfairness of banking fee structures:

Ever get so broke that the bank charges you money for not having enough money? The bank calls up and says "Hi, we're calling because you don't have enough money." And you go, "I know!" So they say, "You have insufficient funds." "Yep, that's a good way of putting it too, I'd agree with that. I find my funds to be grossly insufficient." "You only have $20, so we're going to have to charge you $15." Fifteen dollars, that's how much it costs to own $20. But here's the fucked-up part — now I only have five. Now I don't even have the money that I paid to have.

I think Tanenbaum's joke is a good example of this sort of humor.

Correct. "Joke" as in "funny statement that made me laugh."