In the video's description, Robb explains the circumstances leading up to his eruption:
This girl came up to me and harassed me 3 times while I was playing. She was upset that I wasn't paying enough attention to her and her friend dancing on stage. Rubbing herself on me and yelling in my ear. The first time I was very polite. The second time I was firm and told her I'd be rude if there was a 3rd time. What you see in this video is the 3rd time and final time. I was in the tail-end of a layered 3 minute mix with both volumes at 10 and she came over, pulled on my headphone cord while yelling at me.