Sam Rubin is not having a good day ... and it just got worse.
Hours after the KTLA reporter got his ass REAMED by Samuel L. Jackson for mistaking him for Laurence Fishburne during a live interview, he tried to take TMZ to task for the way we covered the story.
Problems is, TMZ doesn't like being taken to task ... especially when we're right.
That's when Evan stepped in and engaged Rubin in an enlightening civil discussion about their respectful disagreements ... just kidding ... THEY WENT OFF ON EACH OTHER!!!!!
It was all out war on "TMZ Live" .... ya gotta check out the clip!!!!!