No, the wearing of the Muslim veil is not by itself harmful, because it does not hurt anyone. The vast majority of terrorists are men. There is nothing wrong with a woman wanting to wear a veil because it shows they want to be modest. A lot of Christians need to be more modest. Veils are fine, by themselves.
I do not believe wearing a Muslim veil is harmful. Their veil is a part of their religion and I believe they should be allowed to wear it. Their veil can be compared to other clothe options like a scarf and hat and should not be labeled as harmful in any way. The only time I believe they should have to remove their veil is for their license or Identification so they can be identified appropriately.