I think the business is not being fined because its Facebook page is in English, but because it is not also in French. Well, that's how it works for physical signs on shops: they can't display anything in English (or any language?) if there isn't also a French version of it. There might even be something about the size of the French text, which must be larger than the English version.
French and Quebecois radios also have quotas. I think in France radios have to broadcast at least 30% of French songs. I don't know about that figure in Québec.
So the business in Québec could have had no Facebook page at all, or a French page or a page written mostly in French, but not in a foreign language only...