The man dancing is Mac. He's a closeted gay man, who is finally coming out to those around him, but has struggled with how he is going to come out to his father. His father is the inmate, who gets up and walks out halfway through Mac's attempt to express who he is as a gay man, through dance.

The man who is emotionally affected and "gets it" is Frank. Frank is a dysfunctional father-figure of sorts to the younger members of the gang, which includes Mac. Up until this point he's been following Mac around, trying to support him while he comes to terms with his gayness, but the whole time he just keeps saying he "doesn't get it".

Mac's performance may not have gotten through to his biological father, but his spiritual father Frank finally understands what Mac was trying to tell him about who he is and how he feels, but up until then couldn't articulate through words.