Wrong on two counts!
1) +Bp. Williamson was not anti-Semitic.
2) +Bp. Fellay should not be anti-Semitic, either.
Well, recall that those statements were made by +Fellay the politician attempting to do damage control after Bishop Williamson's interview.
There was that embarrassing interview he gave where they cited some statement of his about the Jews being enemies of the Catholic Church, and he gave that embarrassed grin (that Bishop Williamson mocked).
So ... +Fellay was using mental reservation here, where we could all endorse the statement that "anti-Semitism has no place in our ranks". That should absolutely be true, and nobody's "anti-Semitic" (since we realize that Jews are not the only Semites, and most of them aren't Semites at all) and we allow would welcome all Catholic Semites.
I had sent a message to Brother Nathanael welcoming him to the Church, offering my prayers, etc. ... and, before I forgot, I had meant to make a followup post along the lines of, "Oh, wait ... I forgot myself. I'm told I'm anti-Semitic, so I desplore the fact that you've become Catholic and might save your soul."
BUT ... the effect of the mental reservation did IMPLY that +Williamson was anti-Semitic, and that h0Ɩ0h0αx denial is anti-Semitic, etc. But he didn't say it. He was actually leveraging the Jews' own misuse of the term to give that misleading impression that he was condemning h0Ɩ0h0αx, because it was the Jews who conflated the notions, where h0Ɩ0h0αx truth is anti-Semitic. So, in a sense, +Fellay was cleverly turning their own weapon around against them.