There are "valley of bad rationality" effects here. Most so-called fallacies are in fact valuable heuristics. For instance, appeal to authority and slippery slope are both generally correct.

Knowing about fallacies creates in people the illusion that they can tell good arguments from bad. It lets them refute, in a superficially intelligent way, whatever position they don't want to believe.

Though I do think it's worth learning them anyway, for some people, at least so you know what people mean when they say "ad hominem".