Thanks for the link to that review. It contains lots of good information.
Later, during the student turmoil of 1968, the entirety of the Christian tradition came under scathing attack from Marxist ideologists in the university. Ratzinger suggests that he was naive in assuming that the theology faculties would be a bastion of sanity: quite the opposite turned out to be the case. While his own lectures continued to be well attended and well received, many of his theological colleagues were all too eager to get on the good side of the putative revolution. At this point he began to discover what would later be called "the ecumenism of the trenches," as he made alliances with Evangelical (Lutheran) colleagues who appreciated what was at stake. "We saw that the confessional controversies we had engaged in up until now were small indeed in the face of the challenge we now confronted, which put us in a position of having to bear common witness to our common faith in the living God and in Christ, the incarnate Word."
We disagree on many of the details, and that is why we are still not one. But we agree on devotation to Jesus Christ. Because of this, all Christians should fight on the same side.