Name calling is irrational because all it achieves is making the insulted/attacked party put up mental barriers or react to the name calling rather than the actual substantive point. This can actually mean that name calling can be rational because in the right circumstances it makes the insulted party appear hysterical (i.e. non credible) rather than rational.¹ Essentially all that is required is a couple of people (the clique) to gloss over the fact that the insulted party was insulted and double down on interpreting the response as hysterical.²

However, I would say that name calling is very rarely part of an ad hominem argument³ because usually it’s just an insult. That is, one is much much more likely to find “you moron” (which isn’t an ad hom) than “you’re a moron, therefore you’re wrong” (which is an ad hom).

(I’m not sure how common I think the strawman angle is… got me thinking that bit.)

¹ Consider the “guess two thirds of the average game”. Rationally speaking, if it is credible to believe all your rivals are average then it is rational to guess 0. If you can’t believe all the rivals to be rational, then guessing 0 is typically irrational.

² Yes, I know this sounds really bad. I’ve seen it happen. It is really bad. And it gets worse when you know that the people ganging up on the insulted party are in their thirties and their victims are teenagers. Welcome to the internet. Notice that this only works because the clique don’t behave rationally in the sense of the “rational reading” but instead behave “rationally” in the sense of “what behaviour will best discredit the opposition”.

³ Which is illogical/fallacious rather than irrational, although perhaps these things are so similar the distinction is trivial.