An airport is public infrastructure largely paid for by tax money collected from the citizenry. A McDs is a private business owned and operated privately.

Even if the analogy were valid, if McDs employees on strike committed violence against someone crossing their picket line, it would be both illegal and immoral. Defending violence as somehow being ok because some group is on strike and gets angry at those who aren't is abhorrent.

The airport exists at and is allowed operated at the will of the government and citizens of France of which the cab drivers are merely a small part. No single union could ever claim the exclusive rights to transportation to and from the airport it as their worksite. That's an absurd analogy.