Terrorists can kill a lot of people so France needs to do whatever it can to stop terrorists. If this means infringing on its citizens' rights, then so be it. The French people should welcome this move as it will keep them safe in the long term. Would they rather have their rights or live long lives?
We live in a complex world in complex times. We must find a way to balance the rights of citizens who are good, honest people with the ability to pursue criminals and terrorists. It is not an easy balance to strike, but we must not harm the good people while seeking out the bad.
If spying suddenly became the norm as a way to thwart terrorist attacks where would the line be drawn. Once something starts becoming normal, there is less freedom and people will feel like they're being watched and that is an extremely uncomfortable feeling to impose on people for the sake of security.
No, I do not think France should spy on its citizens in the attempt to thwart future terrorist attacks. I believe that, while spying on citizens could potentially get France's government information about terrorist activity, it is not worth infringing on citizens' right to privacy. Citizens may sometimes say things such as, "I have nothing to hide." in support of government spying, but this is not about having anything to hide. It is about governments prying into information they should not have the legal right to. Warrants are required to search citizens' homes. Why should any government be allowed to search private information without a warrant of any kind?