There are two elements to that question.
First, if there is an abuse by the commissioner, the courts are there to correct it. We see this in other administrative areas. I have given courses in administrative law in my career and have taught this to students.
Second, as far as the substance of the matter is concerned, it is true that simply reading “Exit” over the aircraft door does not make the person become anglophone. However, it is a message that is sent to the French-mother-tongue population. It is as if they were being told that their language was secondary. For young people who see this, it's like drops falling into a bowl. As Gilles Vigneault said, the drop that falls into the bowl and causes it to overflow is no bigger than the others. However, when the bowl is full, it overflows. That is bilingual signage. That's the bilingual announcements in airports and bilingual airline tickets. Why do you think the Inuit have demanded that the airline print its airline tickets in Inuktitut? I went to Nunavut, and my airline ticket was printed in three languages. Why did they demand this? It's because the Inuit population wants Inuktitut to become a commercial language. The same spirit is behind the Official Languages Act.
In isolation, you're right, this case can seem like that of a Don Quixote-like missionary, tilting at windmills with his sword. However, if we aren't careful, if we don't draw a line in the sand to indicate that it ends here, the drops will continue to fall into the glass, and it will overflow.