From IMDb:

"The Wrestler" is the story of retired professional wrestler, Randy "The Ram" Robinson, making his way through the independent circuit, trying to get back in the game for one final showdown with his former rival. The film stars Mickey Rourke and Marisa Tomei.

This is a scene on location for a shoot at a wrestling arena in Pennsylvania (2/9 CZW show in South Philadelphia) where they apparently used real wrestling fans (very rowdy wrestling fans) as extras.

Nice touch with the Guns N Roses tune.