Of course, Irving (kinda sorta) apologized last week hours after he was hit with a minimum five-game suspension for pushing an antisemitic book/film on social media. Many felt the apology fell well short of what Irving needed to say to undo the harm he caused.

Count Stern, who happens to be Jewish, among that group ... the world's most famous radio host went in on the 30-year-old hooper Monday morning during his show.

"This Kyrie Irving is a complete douchebag. I mean what a f***ing ... you know he's a flat earther? He's a douchebag," Stern said.

Then, Howard mockingly imitated Kyrie, saying ... "Just let me hate the Jews. Don't bust my balls. I just wanna go on Twitter and hate Jews. Can't you just leave me alone? Everyone hates Jews. Why ya picking on me? I'm just an NBA player. I don't understand anything. A lot of people hate the Jews. Why ya picking on me? The Earth is flat. I think Jews are lizards. Next question. Just leave me be," Stern said to his millions of listeners.

Kyrie has served three games of his suspension ... meaning if he satisfies the team's requirements to return -- meeting with Jewish community leaders, etc. -- he could return this Saturday against the Clippers in Los Angeles.

Even if he returns, Irving reputation has suffered a massive blow ... as have his pockets.

Nike suspended its lucrative partnership with the Nets guard and halted the release of an upcoming signature sneaker.

It's not the first time Stern's gone after a celebrity who made offensive comments. Just a few weeks ago Howard compared Kanye West to just about the worst person possible ... Adolf Hitler.

"Kanye used to be fun crazy. Now he’s like Hitler," Stern said, also calling Ye a "douchebag."

A couple weeks after Stern made the comments, Kanye responded while on a podcast, telling him to "shut the f*** up," adding, "I used to be a fan of you."

Unlike Ye, Irving is yet to fire back at Howard.