I think sometimes in an informal context it’s worthwhile to realize the other person is not a credible source arguing in good faith. The amount of effort it takes to discern and counter bullshit is way more than the effort to just make shit up. Sometimes you don’t want to spend an hour researching to refute someone’s lies.

In that case, “You’re a dishonest person arguing in bad faith” is appealing, reasonable even, despite attacking the person instead of their statements.