Wearing the niqab implies that all men are predatory
Just as locking our doors at night doesn't imply that all members of society are burglars, wearing the niqab doesn't imply that all men are predatory.
The Islamic worldview recognises that attraction between men and women exists and, if left unharnessed, has the potential to break down the moral fabric of society. It also acknowledges the physiological and physical differences between men and women and therefore Islamic legislation for dress and behaviour reflect these differences and aid adherents to avoid situations that could lead to extra-marital sexual relations. Hence both men and women have been commanded to lower their gazes and given directives on dress.
The niqab poses a security risk at banks and airports
By simply going to the side and showing their faces and ID to female members of staff, Muslim women who wear the niqab, have been, for decades, passing through airport security in major airports all over the world without cause for security concern. The same sort of arrangement can be made for any situation where ID needs to be checked.
Niqab wearers can't possibly be teachers.
There are many highly qualified and experienced Muslim teachers. A Muslim teacher, who wears the niqab, would not need to do so if men were not present, therefore many female Muslim teachers choose to teach women or children and uncover their faces whilst teaching.
Banning the niqab will free those Muslim women who are coerced into wearing it.
Banning the face-veil would be totally counter-productive: it would cause many Muslim women to feel targeted and persecuted and is likely to cause many talented women to withdraw from society. The majority of niqab-wearing women in Europe, wear it out of personal choice, so if, for the sake of a suspected minority, the niqab was to be banned, this would be clear discrimination against the majority. If we want to empower women from any community who are oppressed or abused, effective public services where such abuse can be reported need to be made more available and accessible to the women involved.