Muman, I don't believe in women or men dressing immodestly. Those girls in that slut-march are idiots. But I think it's a stretch to say a woman who dresses that way is immoral.
We live in crazy times. Do you have sisters? I think it's much more complicated than you think. Aside from Orthodox Jews, and very observant Christians there is a tremendous amount of peer pressure for girls to look a certain way, and for them to be sexually active. These days, if a women in her 20's still happens to still be a virgin, she is treated like a freak of nature by other women, and doctors too. Any man who would have been otherwise interested in her would usually dump her immediately.
Furthermore, I know all about not placing stumbling blocks before the blind. Women who seduce and sleep with married men do just that. So for them, I have no sympathy whatsoever.