Sure, if you stop something early you may have overstepped, but no one questions violence taking place when rocks are being thrown. Same goes for once a discussion degrades to ad hominem attacks/insults.

You may call something an insult or an ad hominem as a third party, but you cannot know what value the consenting parties are gaining from the fight.

If you claim that you do, you are asserting that you know better about their experience than they do.

I’m not saying there is no room for third parties to intervene, but I question the judgement of anyone who thinks it’s that easy.

There are good reasons why people choose to engage in combative dialog, although it may not be obvious to observers.