Isolation because of language is something fairly unique to Francophone areas, you see the same in Belgium.
Quebec is near the bottom of the pack when it comes to per capita GDP, close to the Maritime provinces and that's including all the government entities present there.
If Quebec would let go of the 'French first' mentality it would likely recover at some point in the next two decades but creating this barrier to commerce has not served it well.
This is in the end not about having the sign in both French and English, the government can do with its signs whatever they want with their signs. They are telling people what to do with signs that are not theirs.
There is no 'protection' to be had from signs, nor is it a sign of disrespect to have a sign in English only.
There are plenty of 'English only' signs where I live and it's neither French speaking nor English speaking and nobody actually cares because they don't see it as a sign of disrespect or feel that they need to be protected.
If the Quebec government would combat corruption and actual crime as zealously as they go overboard on how-high-the-lettering-on-your-English-sign-is then Quebec would be in better shape already.
As for the last part of your comment: it isn't a big deal, that's the whole point, so don't make the language of a sign into a big deal. In fact, don't make language into a big deal. There is no need to protect it, it will change over time and fighting that will hurt you more than that it will help because of the inevitable isolation it will cause.
One hint: nobody spoke 'Occitan', that's a modern artificial construction, based on a unification spread after the languages were already dying (such artificial unifications can work, like in the case of Basque, but this one never took off). The languages were different from an area to another even though they shared a large common root, and even different from a valley from another at my place, where communication is difficult for geographical reasons. So just imagine the differences across the supposed 'Occitan' area that occupies half of France, on areas that were not under the same rule and had no peculiar communication! I remember the reaction of my old uncle from the center of France, the day some of those activists told him he was an Occitan speaker: "what the heck is that? We never spoke it. So now we are supposed we were speaking Occitan? Like the people from the South? First news!" What's funny is that most Occitan activists I met are not true speakers: they learned it as a foreign language, if I may say so, and it shows! they have a terrible French accent when they speak, and they use typical French turns of phrase (as when I speak and write English :-) ).