Social shaming also isn’t an argument. It’s a demand for listeners to place someone outside the boundary of people who deserve to be heard; to classify them as so repugnant that arguing with them is only dignifying them.
Nobody expects this to convince anyone. That’s why I don’t like the term “ad hominem”, which implies that shamers are idiots who are too stupid to realize that calling someone names doesn’t refute their point. That’s not the problem. People who use this strategy know exactly what they’re doing and are often quite successful. The goal is not to convince their opponents, or even to hurt their opponent’s feelings, but to demonstrate social norms to bystanders.
the point is that the active ingredient isn’t persuasiveness, it’s the ability to make some people feel like they’re suffering social costs for their opinion.