You ever hear this one? "He's good people."
I've been around folksy folks who like to say things like that. "I sure like ol' Buck Chapman. He's good people." Or, "That Slim T. Pronghorn feller sure is good people. His brother Lefty is good people too. They both are. They'd give you the shirt off their back any day of the week, and twice on Sunday." Or even, "You know who's good people? Cactus Jack Skalkaho. I've known CJ for a lotta years, and I've always said he's good people. It's too bad we can't all be as good a people as he is."
Don't get me wrong. I like old-timey, 19th century Western Americana-type stuff. On a scale where 1 is stubborn tradition and 10 is extreme progressiveness, I'm probably about a 1 1/2. No, make that 1 3/8.
I know there are expressions that don't conform to the usual rules for singular/pluralism. In Turkish, when you want to say "good day" (at a greeting or departure), the words you'd use translate directly as "good days." We sometimes speak of politics as a single thing, when clearly the word is plural. "The media" is likewise technically plural, but often used in a singular sense.
...but I don't care about any of that. I think calling one person good people is about the dumbest sounding thing you can say. Please don't ever say this around me.