I agree with Sammygol.
My hostility isn’t toward Yiddish. It’s toward the idea that it’s a lashon hakodesh, with is against shas poskim. Mitzvos have a mekor. no mekor, no mitzvah, no matter how nostalgic you are for it. I say pink bandannas are now holy, and everyone has to wear one. Mekor? none, but if you attack it I will lament the “hostility toward this holy mitzvah”. The Torah doesn’t work that way.
There were 4 main dialects of yiddish, northwestern, Southwestern, northeastern, and southeastern- Polish, Ukranian, Lithuanian, German, etc. Some had more Russian words, some had more Polish words. Which one is holy?
Rav Dovid Cohen’s book was meant as aggada, not halacha. The Rambam says Hebrew (both lashon chachomim and lashon Tanach dialects) are holy. He says nothing about any other language. I have yet to see a psak of his that it is a full mitzvah to speak yiddish, and if he does, he is going ahgainst Rav Moshe Feinstein ZT”L who was much bigger. Why are the words of Rav Moshe Feinstein ZT”L not enough to establish what is and what isn’t a mitzvah?