Andy Naylor appears convinced it was completely accidental. As did the referee...
I agree, I can't see anyone believing it was accidental, but clearly some people do.
I think it's one of those incidents that if you've never played, you could think it was accidental (such as Naylor etc. saying stuff like 'he was looking at the ball'). Anyone who has played the game will know Barton knew what he was doing because in that moment you sort of instinctively know...