The business about headwear has little to do with religious beliefs and a lot to do with culture. Catholic nuns until recently wore head coverings that were considered reasonably normal a few hundred years ago. They have now loosened up somewhat. Covering the hair for women is also part of the culture of some Jewish orthodox sects.
The French stance, which I believe is correct, is to ban the covering of the face (not the use of head scarfs or other hair coverings) . I am not allowed to go around with my face covered or, for that matter, to carry a traditional arm, say a sword, on the grounds of my religious or cultural beliefs so why, in the name of political correctness, should we accept it from other residents who are in effect often guests.
When there are only a few immigrants they do their best to conform to the standards of their host country but at a certain point the number arrives at a critical mass where they form their own communities and cease to accept the standards and culture of their host country. At that point some strong minded characters start to force the old culture onto the original settlers as well as the new arrivals. The next step is to feel that we have it wrong and they have it right. This is used to justify crimes against women and acts of violence against the host country.
The irony of all that this is that they want to escape the problems of their country of birth but eventually import the same problems to their host country.
Criminals should not just be interned, they should be returned to their country of origin and totally banned from re-entry to Europe.