A little Wiki background on the dude that The Pope has seen fit to reinstate.
Williamson is viewed as being at the hardline end of the traditionalist spectrum, though he does not go so far as to espouse sedevacantism. He opposes compromise with the Vatican, accusing it of deceit and of being under "the power of Satan" and judges reconciliation between the Society and the Holy See to be impossible, noting that some SSPX members might refuse to follow the Society even if an agreement were reached. Williamson holds that the SSPX is not schismatic but the body of genuine Catholics that keep the "complete faith".
Williamson holds strong views regarding gender roles and dress. He opposes the wearing of trousers or shorts by women and has urged more manliness in men.
Williamson supports conspiracy theories regarding the assassination of President Kennedy and the collapse of the Twin Towers, denying that the latter were terrorist attacks but were instead staged by the U.S. government.
Williamson has expressed controversial views about Jews. He called Jews "enemies of Christ" and urges their conversion to Catholicism. He claims that Jews and Freemasons have contributed to the "changes and corruption" in the Catholic Church. He has also stated that Jews aim at world dominion and believes The Protocols of the Elders of Zion to be authentic. Williamson has denied that he is antisemitic, stating that he goes against "adversaries of Our Lord Jesus Christ", that not all Jews are such, and that he also attacks other groups such as Communists and Freemasons.
Williamson has been charged with Holocaust denial. He has denied the existence of gas chambers and has claimed that not six million but 200,000 to 300,000 Jews perished in Nazi concentration camps. Williamson has also praised Holocaust denier Ernst Zundel.
Now that you've got some background above and beyond the oft' mentioned Holocaust denying, what's up with this decision on the part of Pope Benedict XVI, anyhow, and does it make anyone besides myself not only extremely irate but more than a little bit nervous as well?