You were not taught well. You were raised Catholic, went to a traditional seminary, and yet show a constant naivete about Judaizers and cryptos. You were not formed well. Part of this, I'd think, would have to do with Bishop Williamson himself having had a defective formation, which is why he saw nothing odd in inviting a rabbi to speak to seminarians. He was also a fan of Valtorta, and took that nut DawnMarie seriously. I like Bishop Williamson's good qualities, but he had some defects.
I'll agree with you in disagreeing with his take on Valtorta, DawnMarie ... and I'll throw in Garabandal for good measure. I just don't see any harm in getting to know the other side. It's akin to reading, say, the Communist Manifesto. If you're going to read that and become Communist ... then it's probably good that you got weeded out of the seminary now.