It's not blatant racism but here's the thing...if half the ep had been dedicated to French culture and language, would she have made this post? In fact, had it been dedicated to ANY Caucasian culture, I would bet every penny I have that she wouldn't have made this post.
If anything she probably would have thought "Oh how cool and forward thinking! Maybe my son will remember some French words!"
But she chose to post on Facebook about it because it was Mexican culture, and in her mind that is tied with liberal immigration views and people "stealing our jobs" and other crap like that. Just as I'm sure she would've had an equally ignorant reaction to episodes dedicated to African or Middle Eastern culture.