My previous comment might seem tongue in cheek, but I was thinking along the lines of dispersing the crowd, or distracting them, like you would shoo a flock of birds.
I strongly feel that the bullies actions should be punished. There should be a consequence. Next time it happens, and it probably will if their egos were inflated after this incident:
1. call the cops right away. you never know it might escalate and the big guy might have a baseball bat in his car.
2. take pictures . you need evidence. (think like a detective).
3. ask the cops to punish them somehow
4. give pictures (without victim) to club owner and demand they be banned from the club. Maybe he can post the pictures to humiliate the thugs.
5. tell the victim to carry mase so he can defend himself next time.