Jothar, You need to decide… are you arguing on the Chasam Sofer and Kuzari, or do you support Yinglish instead if Yiddish? You are taking two opposite positions.
In Lita they spoke Yiddish. And I’ve repeatedly quoted that it was a divrei chol, as per the Chasam Sofer and others. Reb Moshe, who spoke Yiddish himself, never opposed Yiddish just brought up the issue of names. Forget the argument over whether Yiddish is “holy”, that side point is irrelevant to the discussion.
Even though there are Yiddishistin who speak Yiddish, they took it from us, not vice-versa (as is the case of Modern Hebrew), and since we do not live in a country or society dominated by Yiddish-speaking shkotzim, there is no benefit of Lo shinu es leshonam by not speaking Yiddish. But there is such a benefit by not speaking Hebrew.