The hostility is not directed toward Yiddish. It pertains to the silliness in calling it holy, and in advocating its usage, especially when most of the frum world does not speak it, and those who do, don’t do so all that well, for the most part.
Compare it to the reaction that would be generated if one suddenly started amusing the public with the notion that we should revert to horses, instead of cars, because they were used for centuries, more holy Jews of immense caliber sat in carriages than will ever be driven in cars, and because a horse has an intrinsic kedusha, due to the fact that Dovid Hamelech rode one to battle his enemies. Besides, there are enough bubbe maaelach about some holy horses flying at night to unknown towns, carrying tzaddikim to perform unspoken miracles, and NOBODY, and I mean NOBODY ever spins such grand tales about motor vehicles.
Horses, water carriers, outhouses, tregers, hand plows, wind mills, …. and some languages are all anachronisms, and, while can be used for nostalgic purposes, have little else of value remaining.