'Cleveland Show' Star -- Kevin Hart Needs To Lay Off Jameis ... He's Just A Kid

Kevin Hart shouldn't have called out Jameis Winston ... so says one of the stars of "The Cleveland Show" who says the QB isn't a bad guy -- just a "bonehead kid."

TMZ Sports spoke with Corey Holcomb -- the comic who voiced Robert on the sitcom -- who tells us Hart was too hard on the guy this weekend when he told him to stop "doing dumb s**t."

"He's an immature kid," Corey said. "He's in college ... he's supposed to have fun."

Corey says most people do "bonehead stuff" in college ... and Jameis is no exception. He just needs to grow out of it.

Still, Corey does have some advice for the Heisman winner. Check out the clip ...