I think it's a delicate issue. The comparison with wearing a kippah or turban in public is ridiculous. The problem with the niqab in this context is that it is more than religiously identifying clothing, it's that there are certainly some women who are under considerable pressure to wear it.
Undoubtedly, there are many women who choose to wear it as a sign of their stronger piety, too.
But the difficulty with wearing a face veil in a western setting is that culturally, covering the face is seen as a negative thing - people wearing masks in public are rarely acceptable.
So this seems to be, at base, a difficulty arising out of a cultural clash, and therefore an integration issue.