It makes me laugh when I see him do that. It's completely over the top, but harmless, and IMO a compliment to his opponent that it meant so much to seal the victory.
I don't get the criticism that it "lacks class". So what if it does? It's not an application to send his kids to Eton.
The important thing is that he's not disrespectful to his opponent, and I don't think he was. Everything else is just picking on a player you already don't like for some spurious, made up morality.