'Patriotism' is to 'Country' as ______ is to 'Language'

Solution 1:

The word chauvinism could be used aptly in such a circumstance along with a suitable descriptor. Note that it is usually used in a negative light.

Chauvinism refers to extreme prejudiced support for some cause.

So, linguistic chauvinism for language would be similar to patriotism for country.

Solution 2:

I couldn't find a single word, but a good example of what you are describing are the Gaelic language revivalists in Ireland. The term that appears most often is "language enthusiast". See below

https://en.m.wikipedia.org/wiki/History_of_the_Irish_language

Solution 3:

I don't know if this works for all languages, and it doesn't quite fit your phrase with the blank, but Yiddishist works specifically for Yiddish.

Yiddishism: a movement characterized by advocacy of the Yiddish language and culture

(The advocacy is needed because Yiddish is dying out.)