You could be wearing a modest, classy dress and a perfect coif in public, but a muslim would say you are showing your arms, legs, face and hair, so you are inappropriate and even sinful! A good illustration of this is how much of American society finds it inappropriate to show your breast to nurse a child in public, but muslim women do not cover their breasts when nursing in public. It is OK in their religion to show your breasts, but not your face or hair (for women). Seems backwards to us, but it is the norm for them.
Not essentializing or pulling an "us" vs. "them" thing would be cool. Thanks.