We need to develop a mindset that the way the world dresses these days is not only inappropriate, it's sub-human and unusually weird.
Rabbi Bentzion Shafier from theshmuz.com gives a mashal to this. Imagine you're hiking in the woods and you smell a nice aroma. You walk a little more and you find Joe. He offers you a piece of meat and you ask what kind of meat it is. Joe answers "it's leg." And you say "leg of lamb?" He replies "no, leg." You ask again, "leg of veal?" Joe says no, "you know leg, like the two legs you're standing on now. You gotta make sure to get these legs when they're young and juicy, mmmm good!"
Now, just as you would never ever have a piece of Joe's mountain meat because it is so far off and unusual, this is the same attitude we should have when developing an attitude to the mode of dress today.