There is, of course, a kind of tradition in Western society that anyone wearing a mask on the lower part of the face is up to no good (which is why most superheroes wear full face, cowl or domino masks). I think it might come from all those images of cowboy bank robbers wearing their kerchiefs as masks. These things hang around in peoples' minds even when they don't realise it.

Me? I look back with longing to the good old days when you had the right to protect yourself from other folks germs with a nice, healthy, natural cloud of tobacco smoke!