If it matters that much to you, maybe you should find out if they respect themselves rather than making a snap judgment about it by the way they dress.
Instead, you're judging them by the way they dress, which is the precise reason clothes have certain stigmas attached to them in the first place. You are making them objects instead of people which is the very root of the problem. It is a not-too-distant extension of this reasoning, by the way, that gives credence to the ever so popular "look at what she was wearing, she was asking to be raped" line of thought.
I know plenty of polo-shirted, khaki-clad women who loathe themselves and plenty of skimpily-clad women who are supremely respectful of themselves. The two things are not necessarily related.