Arguing in bad faith is advantageous because your arguments are able appeal to existing biases or emotional responses or “common sense.” Those biases, emotional responses, and “common sense” are by definition conservative and populist and so they hurt marginalized groups and stand in the way of progress. A rational debate requires a certain level of disconnected and objective reasoning, which bad faith arguments do not do. It also requires the principle of charity, where you interpret your opponent’s argument in the most charitable way rather than rejecting it outright or latching on to some detail they got wrong. Bad faith arguments don’t do that either.

This is why uneducated people and people with limited life experience are more likely to be conservative as well, they only know the default culture they absorbed through their existence, and new ideas are scary. They’re scary for everyone, at first, but progressives are just people who have become accustomed to them and allowed their knee jerk reactions to succumb to reason.

If your goal is to win an argument, then using bad faith offers no advantage.

If your goal is just to do whatever the fuck you want, to not reveal (or possible even have) your actual motives, or to badger people into giving up the exchange, then arguing in bad faith is highly resistant to considered arguments and offers a never-ending supply of counters.