Pet hate

People who misuse "ad hominem" to mean "you just demolished my stupid fucking brain-dead argument without mercy, and along the way cast aspersions on my intelligence which frankly I fully deserve".

An ad hominem argument is when I say, "Well that's the kind of thing I'd expect a Lutheran like you to say", thereby implying that the fault in the argument derives from the fault in the person advancing it. If I say, "You're wrong because the Earth in fact orbits the Sun, you pointy-headed Latin-spouting prancing dimwit" that's not an ad hominem argument, it's a killer point followed by an insult. Ad hominem is not the Latin for "you hurt my feelings".