Creative Minority Report has an excellent post on the controversy over Bishop Williamson of the SSPX.

Bottom line: Responsibility for this scandal rests with Bishop Fellay and the SSPX, who have known for years that Bishop Williamson was unstable. They should have censured or expelled him long ago. And since this scandal broke, they have left the pope twisting in the wind. While Bishop Fellay has apologized and ordered Bishop Williamson to “taking any public positions on political or historical questions,” he remains a leader of the SSPX in good standing. Their inaction has not only embarrassed the pope, it has made the society a source of mockery and derision and endangered its future. Now that the pope has allowed any priest to say the traditional Latin Mass, and these Masses are becoming regularly available in parishes across the world, why would anyone want to seek this Mass through a society whose leadership includes a Holocaust-denying, 9/11-denying bishop?

It is their responsibility of clean up their own house. They can do so by expelling Bishop Williamson.