Make no mistake -- it's not even remotely cool to do this to another person who's sitting there, but kudos to this fan for at least staying to the beat, inebriated as he appears to be.
Then America happened.
By changing his chant from the objectively awful "Seven Nation Army" to "U-S-A... U-S-A" he made a statement about this wonderful country. One where you can have a beer, thrust your groin in another's face and he'll just ignore you, quietly sipping his beer. This is so much better than a brawl.
Wait... are you still a patriot if you groin-thrust the face of a Patriots fan?