Xinhua is the official news outlet of China; they're China's Pravda. They aren't doing Snowden any favors in the US by writing this, but, of course, that's not the point.
I agree that they are not doing Snowden any favors by writing this piece. It makes him look more suspicious. They should just shut up and watch the show.
Why would they want to do Snowden any favors? Their best move is to be very vocal, and milk the scandal for all its worth.