That’s the only conclusion one can come to, I think, and that’s the one Fr. Jim Martin arrives at in his post examining a sampling of the “gibberish” (Cardinal Kasper’s words) on the SSPX sites.
Fr. Martin links to one article in particular, from 1997 but still up on the Society’s American website, titled “The Mystery of the Jews.” It is embarassing to have to point out such stuff (as Martin says, it reads like “Mein Kampf”). But sunlight is the best disinfectant, as they say, and the only way to convince some SSPX-deniers…
Herewith a few gems:

“It is public knowledge that the Jewish sector, relatively small compared to the Gentile sector which devotes itself to the creation of wealth, controls especially the financial power that is exercised through banks.”
“Then these Jews, in the name of their Law, their Torah, and to serve the material interests of their nation and race, demanded the blood of Him who had been promised them as their blessing. They stirred up the Gentiles against Jesus. Using them to carry out their plans, they crucified the One who was to be raised up as a “sign of contradiction”.
“Judaism is inimical to all nations in general, and in a special manner to Christian nations.”
“Catholics are not to enter into commercial, social, nor political relations which are bound hypocritically to seek the ruin of Christendom. Jews must not live together with Christians because this is what their own Jewish laws ordain and also because their errors and material superiority have virulent consequences among other peoples.”

As mentioned below, John Allen and others have pointed out that this anti-Semitic or anti-Jewish stuff is a trait running through the Society, and dismissing it as a product of just Bishop Richard Williamson’s YouTube ravings is not kosher.
In any case, I list Father Martin’s post first, thinking doubters may be willining to listen to a Catholic priest. For a full report, though, check out the ADL’s report, titled, “The Society of St. Pius X: Mired in Anti-Semitism.”