This case is purely a personal matter between Xiao and Fang, and they are fighting for some meaningless stuff (at least from the point of view of an outsider). Xiao is not a big corrupted scientist, there is nothing solid that Fang can accuse of him. It's actually very similiar to a fight between two mad women...
There is no need for that Yush's stupid letter. What does he (or she) want? Xiao has no serious problems worth denouncing, so this yush wants to have people united to oppose the justice of China? Naive.
About Fang: There are his golden days when he was the first to pick out those cheaters in academics of China, and at that time there were many people (decent scientists) supporting him (it's said that Xiao was once a supporter of Fang). But look at who are his fans now? A group of 网络愤青and 民运分子.
I think we should thank Nature to have given a very good definition of the nature of what Fang and his XYS are doing now. Maybe before Nature published the Cultural Revolution picture and the article, many of us didn't know exactly what went wrong with Fang's DAJIA. But AFTER those were published, the crazy posts on XYS have definitely shown us how correct Nature is... see those ugly posts attacking Prof. Fu, Prof. Qiu, etc... also those meaningless posts attacking the editor of Chinese Geographic...
Now the only thing I like Fang about is his popular science articles. Very well written. He has good training in science and a rare capability in writing. To be a popular science writer should be his correct career.
But don't rely on a group of 愤青and 民运. That will ruin your reputation and your whole career.