The article is quite interesting, but I have to say I don't understand why Yiddish being a Slavic language would suddenly mean that all European Jews are Iranian; the Slavic languages aren't descended from anything spoken in Iran in the first century CE. That really feels like it came out of nowhere.
I wonder why anyone would think that. The words predominantly come from German, and the grammar is more of a thing of its own, far from resembling anything Slavic...