In my experience, it's most important to give them a path to leave their position without losing face.

Many times, it may look like someone is arguing in bad faith, even though they're really just wrong about something or may even just have a different perspective on things.
If you approach them by saying "Hey, this is a common misconception, here's why it's wrong." or "Hey, my experience is like this, is yours different?", then they can easily come back around and learn from you, or teach you something.
If you're assuming they're arguing in bad faith, chances are, they think the same of you, so breaking that up before you try to bring in your best arguments, is in the interest of everyone involved.

For the rare cases that someone is genuinely arguing in bad faith (i.e. trolling, really), I find it most effective to make it clear that you're not personally invested in them not being an asshole. If they want to be intolerant, so be it.
But that does not mean that you tolerate their intolerance. If they're intolerant, they break with the social contract of tolerance and will be treated as lesser.
That way, you:

• nix the fun of trolling you.
• make it clear that they're being dumb.
• give them a clear path out of there (i.e. simply not being an asshole).

You can if others are paying attention. You can get the other person to display their true selves. So you can convince a third party, and furthermore it can create peer pressure for the bad actor.

Further, you can decide to focus on the sycophants surrounding them. They're generally in this follower mode and if you play you cards right their support will buckle.

Especially effective if you combine the two.

Interesting question. Funnily enough, i‘ve been asking myself about bad faith arguments a lot since the last couple of days. Seems like lemmy is getting run over again.

I personally dont immediately detect bad faith arguments so I always treat them like normal arguments. People then often get really annoyed at me, probably because they wanted me to be outraged or shocked. Then they lose it which really amuses me.

Calling out if I detect something like it has also helped. „So you are saying a group of people deserves to be abused and ultimately killed?“ to stay with satre‘s example.

Have a good one.

If someone's being bad faith just clown on them. They're not going to take it seriously so why should you?

I like to out-crazy them. Of course you wouldn't want to do this in an anti-Semitic way, but there are plenty of ways to troll them with crazy, bonus points if you can get them to agree with you. For instance, if they say that they think that vaccines cause [medical condition], counter with vaccines are a hoax perpetrated by the State of Oklahoma in order to get more Federal money and to further the Liberal Woke™ agenda.

Hard to maintain if someone is pushing all the right buttons, but I have found it most useful to treat every argument as if it is being made in good faith.

Sincerity is impossible to “prove,” so any attempt at calling someone out is doomed; best (imho) to engage the point and not the person making it.