The Leaden Rule.
As a correlary to the traditional metallic rules of behavior, I’d like to advance my own: insult your opponents only by standards that you consider fair and shameful breaches of behavior. Shoot honest lead, in more metaphorical words.
A lot of people don’t do this. And when your stated causes are to fight against the prejudices of people who aren’t rich, conventionally attractive, or neurotypical, turning around to snipe at the neckbeard sperglord living in his mother’s basement makes your concern look less than sincere.
We insult people to hurt them, generally. We can also do it to show virtue to our in-group, or as a kind of public performance art that no one takes seriously or personally, but mostly, people insult other people to hurt them. And when you want to hurt them, it is very tempting to look carefully at them, and identify their weak points. We all want, in the heat of a battle, the silver bullet that puts down the werewolf, after all.
But werewolves don’t exist, and arguments aren’t bullets. (Barring extreme edge cases in regimes with very short gaps between condemnation and arrest, of course.) Giving up your principles and aiming hurtful remarks at your enemies, by a standard you yourself disclaim, is like melting down the family silver to go hunting monsters; you’re giving up an old and cherished resource in the form of your integrity and good name, when you have no evidence that the monsters you’re shooting at are actually movie werewolves in the first place.
And where does following the Leaden Rule get us? Well, it gets me to the point where I pause, delete an angry screed, replace it with “I think you’re overexaggerating the statistical significance of a few outliers here.”, and when I get a reply that consists of “lol dont care”, am enlightened. I realize that nothing I could say to the person I want to insult is more actually insulting than what they’re saying of their own accord, and that my work here is done. I further realize that any further interactions with them in this vein is pointless, and so withdraw, and manage to both secure my own peace of mind, and not end up compromising my own principles for the sake of a meaningless Internet dust-up.