Are they slutty? Sure. Do you have a chance in Hell of getting your wife/girlfriend to dress up in one of those? No. That's not the point. Okay, maybe it is, but besides that, it allows us guys an opportunity to, how shall I say, enjoy the aesthetic beauty of the female form in all its soft, curvaceous glory. Is it okay to think of a girl who wears one of these sexy? Yeah. They got dressed up to look sexy. There's nothing inherently wrong with that. Just don't be a creepy stalker who follows the girl around during the party or tries to get down her pants. You are not dressed up as a skeezy rapist for Halloween, and if you are, what the fuck is wrong with you?
Anyway, for all the ladies, let me make a few suggestions for Halloween costumes:
As for the guys, all I ask is you don't wear those retarded costumes that have some kind of crude sexual innuendo to them. I'm sorry, but dressing up as a snake charmer with a snake coming out where your dong should be or wearing a lab coat that has "Dr. Seymour Bush" on the nametag will not get you laid, no matter how many beers she's had.