Khloe Kardashian -- OJ's NOT My Godfather ... Not All Black People Look Alike!!!

Khloe Kardashian is pissed at some of her "f**king stupid" Twitter followers who have a hard time telling black people apart -- and it's all over a picture of Sugar Ray Leonard.

The drama began when KK posted a pic for "Throwback Thursday" today featuring Robert Kardashian, Bruce Jenner and Sugar Ray -- and said, "#TBT I love this picture! My daddy. My second dad. My God father."

But some people confused Sugar Ray for OJ Simpson -- a friend and client of her father's -- and clearly, Khloe no likey.

"For those of you that are that f**king stupid.... That's NOT OJ in my #TBT," Khloe tweeted ... "That's Sugar Ray Leonard. Some of you never fail to amaze me!"

On a related note ... Bruce sure looks different these day, huh?