EXCLUSIVERay J used another one of his appendages early this morning to take care of business ... this time beating down a dude in a violent confrontation that started when Mr. J called a woman a "fat bitch."
It went down at Club Nokia in downtown L.A. at 1 AM, after Mack 10 and Jamie Adler's West Coast Fest concert.
A woman goes nuclear on Ray J ... an eyewitness tells TMZ Ray J hurled the insult at her and she just goes off, screaming, "You said f**k me fat bitch." Ray J tries to calm her down, to no avail.
She has a couple of great lines ... "I'm the bitch they went to go get to whup bitches asses," and "I ain't no fake-ass n****r from Carson (Ray J's hometown)."
It's unclear how the fight started, but Ray J and some dude got at it, and it's pretty clear ... Ray beats the other guy's ass.
No one was arrested.
The woman in the video who's going off on Ray J is Paulie, Suge Knight's niece.