Kevin Hart Cracks Joke About Stefon Diggs' 'Pink Stuff' At BET Awards

Kevin Hart brought Stefon Diggs' recent controversial yacht ride back into the limelight at the BET Awards on Monday night ... with a joke we're sure the New England Patriots would have preferred he kept in his pocket.

As the comedian was poking fun at Diddy onstage at the Peacock Theater in downtown Los Angeles by urging celebs to stay way from "slippery" after-parties ... he threw some shade at Diggs and the NFL star's new girlfriend, Cardi B.

"No yachts, no boats," he said as he implored the audience to immediately take driver-less cars home from the show. "Cardi B -- no pink stuff. What the f*** is that, huh!?"

The line -- of course -- is a reference to Diggs and Cardi's now-infamous Memorial Day Weekend cruise through Miami waters.

You'll recall, while the couple was on the boat with a bunch of bikini-clad ladies ... Diggs was seen on video whipping out a container filled with a mystery pink substance. The wideout appeared to say in the footage he wanted the women to go have fun with it -- and then come back to him.

Hart's jab over the scene grew big laughs from the crowd ... but Mike Vrabel almost certainly wasn't giggling.

The Pats head coach looked disappointed in his receiver when he addressed the matter with reporters on May 28 ... explaining he was "aware of" the clip.

"Obviously, we want to make great decisions on and off the field," he said, "and we're hoping that with our time here on the field today, and that when we don't have a script and we're on the call-it periods, that we're making great decisions."

"The message will be the same for all our players -- that we're trying to make great decisions, and any conversations that I've had with Stefon will remain between him and I and the club."