Huh... I'm an INFP... I thought it was funny. But maybe I'm just stupid. :P
I tend to appreciate "stupid people humor" as well as good, intelligent humor.
I don't know, to me the air of teasing seemed quite obvious... I didn't think it was necessarily to "provoke a response" per se, I thought it was more just to make the other types roll their eyes, and go "Oh, yeah, that's so funny."
That over-the-top bravado thing is how a lot of my friends joke around quite often, and it's more designed to make you laugh at the person than it is to make you laugh at what they're actually saying. What do I mean?
Well, using this example... this person is an ENTP. This means that they are probably a relatively rational person. Most of the statements they make are totally irrational, and in a very exaggerated way. Take this statement: "If you're a good person who can think rationally - you're an NT-Rational. If you're a loser, or a fat person, or someone who cries all the time, you're in one of those other categories." A fat person? That's ridiculous, how could that be correlated with type? If you're a "good" person? That is a totally subjective description, coming from a self-proclaimed objective person. It's basically them making themself sound like an idiot on purpose to make you laugh, and in a manner that is so exaggerated that they're hoping you'll figure out that they're not actually that stupid or ridiculous.
As to the generalizations made... well, they are just that-- generalizations. They are not supposed to be totally accurate. And it's irrefutable that some NFs really are crybabies (even with mud for brains). Similarly, there are some SJs who are mindless zombies, following authorities without question. Same for SPs. And guess what? There really are some ENTPs who are way cool, smart, funny, awesome, and etc. It's just not all of them. But we know that, and that's what [is supposed to] make it funny. Simply the fact that he (or she) is grouping all those people into huge groups with condescending and ludicrous descriptions is totally un-objective, to the point where it's humorous (or is supposed to be).
If you don't appreciate this specific person's sense of humor, that is totally fine-- that's why there are so many different types of humor out there! Just keep in mind that he probably didn't really mean it, and if he was serious, he's clearly an idiot who shouldn't be taken seriously.