Benedict's brilliant little book was a positive analysis of Vatican II, especially it's notions of ecumenism and the nature of the Church. It was not well received by traditionalists, especially Marcel Lefebvre's group. Their contention was that the Church's entire tradition had always stated their was no salvation outside of Catholicism. There were no legitimate ecclesial churches outside of Catholicism, and Catholicism held the total truth about Jesus Christ and his intentions for mankind. This link will take you to an analysis of Benedict's book from the SSPX perspective. The basic thrust of the analysis is that Vatican II was not an extension of traditional thinking on the true nature of the church, but was in direct opposition to tradition, making it a form of heresy.
Like John Wilkins, I see no way for the SSPX to affirm the teachings of Vatican II. Their opposition is the reason for their existence. Vatican II documents do leave open plenty of room for salvation outside of the Church. For Traditionalists there is no such thing as ecumenism, there is only conversion. There is no such thing as Truth outside of the Church, there is only heresy. These are not positions from which one dialogues, they are positions from which one bullies. This is why I think Wilkin's second option is far more likely, that Benedict's open hand signals a shift towards the thinking of SSPX and away from Vatican II.
If this turns out to be true, then Benedict has done exactly the same thing as Archbishop Chaput, gone from a humanist progressive to an authoritarian traditional conservative, and not just liturgically but in his conception of what the Church actually is.
Why, I wonder? Does all of this actually reflect an enormous lack of trust in the People of God, in the power of the Holy Spirit, in the ability of Jesus to work His love within the greater world? I think it does, because one of the hallmarks of a lack of trust is the need to assert authority to maintain a semblance of control. In other words, it isn't about faith in Jesus, it's about a lack of faith in the living Jesus, in the Resurrected Jesus. It forces the Church to operate from a position of existential powerlessness which is then manifested by having to force itself on the flock and the culture in which it is situated. Can anyone say 'Martino'.
The good news is in the end Jesus reserved our final judgement to His hands. Thank God.