It's really best not to engage with people when they want to fight dirty. If you maintain your self-control and behave much better than they do, they'll often find a problem with that, too. You count to 10 before speaking, and they ramp up the yelling because "you have nothing to say" or "you're a coward." You decline to dig into the details on something they claim that's inaccurate, and "you can't argue" or "you don't have a leg to stand on," or else "you're ignoring me" or "you never hear anything I say." You point out the errors in conduct they're making as politely as you can, and you're "condescending" or "up on your high horse." You address logical unsoundness or empirical uncertainty (with or without any fancy words) and you're "egotistical" and "calling me stupid to my face." You agree with untrue things they say to appease them and you feel dirty and dishonest and weak because you were bullied into lying.

There's no winning. Get out. Leave that bullshit atmosphere.

And if you're responsible for that atmosphere: Stop. Improve. This is misery that you're foisting on others and even yourself. It makes you look terrible. Please learn better methods.

Ok, so it is possible to find ways to validate people's carried-away, somewhat abusive angry feelings without outright lying to them. But for that, it really does help if you don't mind lying to them partly, at least by extensive omission (suppressing comment on everything you know is off-base, instead finding something you can relate to so that they can feel heard). It's harder to be totally honest and remain validating toward someone you flat-out disagree with and think is throwing a tantrum, and not even on sensible grounds. It's possible to find compassion for that person and see it their way without actually biting the bullet and agreeing with a lie, some misconception they seem to be clinging to. But that takes practice, training, experience. Basically no one is born with that skill. It's extra. It's nice to have - really, this is a great, amazing, priceless skill, but it's extra. We can't assume everyone will know how to deescalate. The default, reliable solution is: Leave the scene. Just do it. Say why, leave. Don't be mean. Don't be rejecting. Don't get guilted into continuing. Don't defend yourself. Be brief. Be clear. Leave.

It seems hard at first, but it gets easier fast when you see how well it works.