Dressing 'like a slut' is an exaggeration, hyperbole surrounds us everywhere. Not to mention complete abandonment of traditional word definitions. Look at the word gay 50 years ago: homosexual, and now: stupid/uncool as well as homosexual (also associating the two, rather than it being merely immoral). The same thing with slut, both sides of this little argument need to be slightly less literal with these words. The fact that I call my friend a faggot doesn't mean I think he's gay, or a bundle of sticks, or a cigarette, it means I'm joking around and exaggerating a small error of his or some action I don't decree 'appropriate' for our social standards (which are pretty fucked up so I call him a faggot for doing normal things, like helping an old woman with her groceries, or some other moral activity)
Now that I've spent too much time calling you all silly, I don't approve of dressing... Not how you are I guess? I dunno, we do define each other by looks at first glance, if I see a guy wearing a bunch of gangster clothes, like I said before, I don't think he's a gangster, I think he's an idiot and I don't even talk to him because I have that impulse he's got nothing to offer intellectually, whereas that might not be the case, he could be a cool guy with a taste for the rap and no better idea on what to wear.
Likewise with people wearing 'slutty' (see above) clothing, I generally don't associate with girls that wear 4 inch skirts, because they just come off from first glance as... whores, to put it way too far. I'd prefer some pants, mayhaps a skirt that reaches below your waist line, you know, whatever. I can't say I know, but I can say that more girls that dress 'slutty' are not the type of people I want to hang out with than aren't. Hm that sentence was confusing. Whatever you get the point.
Realizing how you dress makes an impact on others views of you is basic common sense, if you don't want to be taken for a 'whore', don't dress like one, dress like... Sexy, but don't overdo it I guess?
The only 'trampy' clothing I really hate are the 4-6 inch skirts and shirts that are too damn small. I can't really think of anything else that I would consciously avoid someone for though. Maybe enough makeup to put a clown to shame, though that's not really catching on with the young women yet.