Michael Rapaport is pissed at Donald Trump -- saying POTUS has forced him to side with one of the people he hates most in this world ... LaVar Ball.
Rap and Ball have been trading shots for months -- with the Hollywood star once famously declaring, "Big Baller Brand shirts look uncomfortable as f**k."
But now with Trump blasting LaVar in the media for not thanking him for getting LiAngelo back from China ... Rapaport is begrudgingly joining Team Ball.
"Donald Trump. You're such a f**k."
"You're gonna take away the pleasure I get from talking sh*t about LaVar Ball?"
Rap says when it comes down to it, he and LaVar are just "talkin' sh*t" -- but Trump's a "threat to society."
Still, don't expect him to rock a BBB shirt anytime soon ...