Michael Rapaport Sues Barstool Sports, I Don't Have Herpes!!

2:38 PM PT -- Dave Portnoy has released a statement to TMZ Sports ... saying “Michael Rapaport is a loser. There is nothing worse than somebody who claims to be the king of trash talk and then cries when people respond in kind."

"Unfortunately as much I’d love to take credit for ruining his career he did it to himself by being an unhinged lunatic. We wish him nothing but the best as he fades into oblivion.”

Michael Rapaport says that sore on his lip is NOT herpes -- and now he's suing Barstool Sports claiming the media outlet and its most famous staffers are defaming him.

Rapaport used to work with Barstool -- in fact, he had a podcast on Barstool's platform.

But, the two sides had a nasty breakup back in February after Rapaport referred to "Stoolies" as "losers in life."

Barstool president Dave Portnoy told TMZ Sports at the time the move was not a publicity stunt -- "To me, it was very personal. It was very real."

Rapaport claims Barstool then embarked on a smear campaign against him -- publicly claiming he suffered from herpes and creating a t-shirt (which they sold) highlighting a sore on Rap's mouth.

Rapaport says some of the staffers -- including Portnoy, KFC and Smitty -- mocked him publicly, calling him names like "herpe having, race baiting, D-list actor" and "old crusty herpe."

Rapaport says he's been defamed -- because he "does not suffer from herpes."