The maharil was asked if one could supply a mezuza to a town mayor who asked for it because he had heard that it brought 'luck'. He replied that one should explain to the mayor that it only brought luck to those who kept what was written there. The reason he refused was because maybe the priest would visit and desecrate it or his children would. The r'mo is more lenient if it is really necessary
My husband owned clothing stores outside of the NYC area. One day he went to a Garment District wholesaler and saw mezzuzahs on all the doors but the owner and employees of the business were dressed in traditional Hindu garments and did not appear to be Jewish. He asked why they had mezzuzahs on all their doors and they told him "its a sign that you are in the garment industry"