Yiddish is a holy language, much like chazal say not to take Aramaic lightly, because so much Torah was said in it.
Germany descended from amalek, as the Gaon said. But no one had a problem speaking a changed version of the language.
Using german products, especially companies which assisted hitler ym”s like Volkswagen and Mercedes, is something people with a Yiddishe heart boycott. Some of my rebbeim mentioned it, that they learned from their survivor parents never to touch a German product.
It’s very offensive when people mock the idea.