No one should be forced to wear or not wear something. It's their body and if they want to cover it so they aren't judged for their looks than let them do it. If you force them not to wear it than your just as bad as the Taliban and Boko haram when they force girls to wear it. The government doesn't have a right to tell people how to dress.
The government has no say in what people of different cultures are allowed to wear. The hijab is a part of Muslim culture. Sadly, it now carries a negative connotation, but that is due to extremists. America is made up of many different cultures and those cultures should be allowed to follow their own traditions as long those traditions do not conflict with American laws and basic civil rights. If the government became allowed to ban one piece of clothing, we may find them digging through all of our closets.
There are a few reasons for this.
1) The government cannot discriminate against a person of a certain religion just because they are that religion.
2) In order for a ban to constitutional, they would also have to ban yarmulkes, cross necklaces, basically any sort of religious item that is worn on the body.
3) Since when can the government say what you can wear?
What harm does wearing the hijab do? Wearing the hijab is part of the Muslim culture and religion. Wearing the hijab does not make one a terrorist. Wearing the hijab is not a crime. There is no reason for the government to interfere with what a person is wearing. The government has no right to strip away a persons culture or religion.