A rep for Penn just released the following statement in an attempt to clarify what happened before cameras started rolling ... telling TMZ Sports, "Upon meeting friends for a concert at the Lava Shack, words were exchanged between BJ and the acquaintance. From witness accounts, BJ tried multiple…

UFC legend Matt Serra claims some drunk a-hole was threatening the servers at a Vegas cafe on July 4 ... so, he took action -- AND TOOK THE GUY DOWN! Serra was chllin' at the Grand Cafe at Red Rock Casino -- the night before he's set to be inducted into the UFC Hall of Fame -- when he saw the…