Look out, anti- niqab activists, you have a major ethical headache coming your way. It's in the form of a new sexual fashion in the Western world. This fashion hides the face completely. It's a product of total emancipation, so you won't be able to argue that it's repressive to its wearers.
You may not have heard the word zentai, but you have probably seen it, particularly in green. For some reason, certain sports fans like to wrap themselves head to toe in opaque skin-tight green spandex suits, complete with featureless facemasks, and show up at National Hockey League games to dance in the stands. This is particularly popular in Philadelphia, probably because of repeated appearances by a hooded, spandex-encased, dancing "green man" on the U.S. sitcom It's Always Sunny in Philadelphia. Canadians have probably seen a couple of such fans at Vancouver Canucks games: There is a popular YouTube video of them harassing an opposing player in the penalty box (it's from Dec. 22, 2009).
The more worldly may have seen such zentai suits at fetish parties, because the wearing of full-body, face-obscuring spandex is primarily a sexual thing (and it's primarily the embarrassingly revealing nature of such a thin suit that makes it ripe for comedy). But increasingly serious zentai wearing is cropping up on city streets, as it is not so far illegal.
The fashion originated, unsurprisingly, in Japan, where the connections between sexual expression and outré clothing, particularly childlike cartoon-character looks, are unashamedly embraced. The word comes from zenshin taitsu: Z enshin is "full body" and taitsu is from the English tights. It's not to be confused with hentai, Japanese comic-book sex art, but you might say it is thematically linked: A lot of people are drawn to the wearing of spandex suits through their emulation of superheroes and other anime figures. The complete, artificial smoothness of the zentai suit does enable one to begin to resemble a computer-drawn image.
Devotees of the style claim various motivations. They say the silky fabric simply feels sexy, or that they like feeling confined by something tight, or that they like the partial sensory deprivation that the reduced vision of the mask gives them, or that the mask enables them to be simultaneously exhibitionistic and anonymous. (This last is probably the most important. Many zentai enthusiasts will claim that there is nothing sexual about it; they are disingenuous, as the quickest of Google searches for zentai will show you.) There is also something liberating about transforming oneself in fantasy into a non-human - some zentai suits are zebra striped or checkered or have a metallic, robot-like sheen.
Zentai fetishism is a cousin of two other costume-based fetishes, also with Japanese roots: cosplay and yiffing. Cosplay is dressing up as a character in science fiction (usually, but not always, Japanese), and many cosplay suits have a spandex component. (An incidental note on terminology here: Spandex has come to be used as the generic term; Lycra is the trade name, owned by Dupont.) Yiffing, a subgenre of cosplay, is sexual activity while dressed in an animal costume (i.e. as a "furry"). All these practices are about transferring one's sexual life onto a fictional character, so that one isn't really oneself while doing it.
Now, while you're shaking your head with disdain here, and thinking it might not be a bad idea to limit all this in public, it's worth considering how much of it is already going on in public. How many enthusiastic cyclists do you know who seem to spend as much time walking around town in their clingy synthetic shorts and tights and tops as they do on the bike path? For many, cycling is merely an excuse to indulge their exhibitionism. And elaborate costumes have always been a part of sex, as a walk through any red-light district will prove. All costumes, when you think about it, are odd. (What's natural about garter belts or, for that matter, bras?)
The tricky part for lawmakers is going to be not only their natural desire to repress sexual expression in public, but the culture's general discomfort around masks. Masks are associated with crime: A guy comes into your convenience store after midnight wearing a face-obscuring hood and you're going to be reaching for the panic button. On a more basic emotional level, just as with Salafist Muslim veils, masks are off-putting. Simply put, they look creepy.
But I have not yet heard a peep about banning these nerdy costumes on any of these grounds. Nobody seems offended by pudgy guys in tight clothes who don't want to show their faces, or worried about the possibility of them indulging in crime sprees.
No doubt some conservative group will spring up and claim that this bizarre costume is somehow threatening to the Western way of life, a rejection of common values, a refusal to integrate, etc. And when it does, it will look silly and paranoid.