Tom Morello -- Breaks Up Screaming Match After Rock Show

Hard to believe a guy from Rage Against the Machine can play the role of peacemaker -- but that's exactly what happened last night when guitarist Tom Morello stepped in between two angry dudes ... and it was all caught on tape.

It all went down outside the Troubadour in West Hollywood -- where legendary acts like Bob Dylan, Joni Mitchell, Elton John and Richard Pryor played back in the day.

Morello was chillin' outside after his show ... when the two guys began screaming at each other .... but somehow, Tom managed to get each side to apologize.