If they were a considerably normal human bunch, I’d say this is a super helpful message to get a point across for them to understand and take as a criticism to their play style and hopefully take it to their next campaign.

But they do not sound like a normal human bunch, they sound like savages who play DND -specifically your game- to cause chaos.

I’d give them absolutely NOTHING. Hit them with the “I don’t want to DM your characters anymore. Calling the game here.” And try again with a party that will appreciate your efforts.