Nostra Aetate was a watershed for the Church's stand on the People of Israel (The Jews). It completely disavowed all the 2000 years of anti-Semitism by Catholics and essentially made anti-Semitism a sin. The ramifications of Nostra-Aetate on Catholic doctrine are still unfolding, but the main thing is that we now see Jesus as a Jew who practiced Judaism. Christ established the Christian Church, which was, at the beginning, a Jewish sect. All the first Christians were Jews who continued to practice Judaism. Thus the Church now sees Jews as our "elder brothers" and Catholicism as the continuance of Judaism. In addition, we see that the People of Israel continue to play a distinct role destined for them by God, that they are not a thing of the past. All I have to say is, IT'S ABOUT TIME!
The thing about SSPX is it's tolerance of anti-Semitism. It's not that all in SSPX are anti-Semites, so much as that Catholics who are anti-Semites find a safe haven in SSPX, where they can go on believing that the Jews are a cursed people, and that Jews as a people are jointly responsible for the murder of God, etc.