I view a Muslim woman wearing a hijab as no different than a Christian woman wearing a crucifix necklace, sporting a rosary bracelet, or affecting plain or conservative dress (e.g. in the case of a Mennonite or the Amish). I don't think religious garb should be mandated by the State in any capacity - either for or against, it should be the personal choice of a person of faith to wear such garb or to not wear it. It certainly isn't passive terrorism, and I think the majority of people think nothing of it.
Also of note, there are several religions that prescribe a head-covering - Sikhism, Judaism, Taoism, Buddism, and several Christian sects such as Eastern Orthodoxy, Mennonites, Catholicism, etc. Are any of them automatically seen as terrorism, even passive? Seems kind of unfair to single out the turban, taqiyah, or hijab.