A really good friend of mine had an interesting habit.
Whenever he was about to point out a defect of someone who wasn’t around, he’d start with “Billy” (or whoever) “is a really good friend of mine but…”

For instance, if Mark had a loud voice and this friend had a need to talk about that, then he’d say “Mark is a good friend of mine but he rattles the windows when he talks”
If Neil was reluctant to spend money, then this friend would say “Neil is a really good friend of mine but you couldn’t open his wallet with a crowbar”

After noticing this a few times, I pointed this out to him.
I said “Whenever you’re about to slam a friend of yours, you always start by saying that he is a good friend of yours. And then you slam him.”
He said “You’re right. I’m gonna try to stop that”

A few days later, a bunch of us was talking about someone else’s failings.
My friend said “He’s a really good friend of mine” He stopped himself, looked at me and started laughing.
Then he said “And I’ll stop there”