Sedevacantist Catholics, Jansenists, and St. Paul

One of the strange marks of Sedevanatist Catholicism today is a certain amount of anti-semite hysteria. The Gibson clan of Hollywood has made it rather famous in the last 20 years, but the coziness of the Popes to the Jews since WWII has been a point of contention that pushes people towards radical traditionalism.

Radical traditionalists are also considered to have some affiliation with the old Jansenist heresy, which was a form of Catholic Calvinism- fierce loyalty to the Pope but hopelessly elitist, they treated the sacraments, especially the Eucharist, more as reward than as Grace, requiring long years of study to be admitted to the sacraments. And certainly, no non-Christian could be saved in their predestined view of the world.

Which leads us to an interesting bit of prooftexting. Could the modern Popes be right about the lack of any need to evangelize the Jews? Romans 11:25-26 seems to indicate so:

25 Lest you be wise in your own sight, I do not want you to be unaware of this mystery, brothers:[a] a partial hardening has come upon Israel, until the fullness of the Gentiles has come in. 26 And in this way all Israel will be saved, as it is written,
“The Deliverer will come from Zion,
he will banish ungodliness from Jacob”;

Perhaps the Jews really are our elder brothers in faith. But then again, we know from Luke 15 what elder brothers are like, don't we?