i'm going to assume that this is an honest question and not a troll, and try to answer this.

The idea that complimenting women on their physical appearance being a good thing is predicated on the practice of viewing women as little more than man-chasers. Basically, that even a professional, educated woman holds as her highest goal landing a man to provide her with hearth and family, and hence, makes significant effort to promote her physical beauty in the hopes of attracting said man. So by making that compliment, you're saying, maybe without even meaning it, "Good job at making yourself up to attract a lot of male attention today!"

Blargh.

Look, there's nothing wrong with sincerely telling the special person in your life that they look great; if they're your special person, they probably *want* your opinion and attention, if not affirmation that you are attracted to them.

You could probably even go so far as to compliment someone on a choice of attire, an accessory, or even that they're looking really sharp or dapper, *if* you have an established casual relationship with the person (but even then, depending on the person, you might be crossing the line, so always err on the side of caution). But anything beyond that is an objectification of a person who has no idea what your intentions are, so by trying to be nice, you may be coming off completely creepy and making them uncomfortable.

Or put another way, let me assume for the moment that you are a hetero guy. Now let's further imagine that you're doing some casual activity, like grocery shopping, and some guy, let's say a big guy, tough-looking, muscles...Hell, let's say Ray Lewis of the Baltimore Ravens is passing you by with his shopping cart. He stops, slowly looks you up and down, and says to you, "I just wanted to say you look really good in those tight jeans, mister." Now, how does that make you feel? You don't know what Ray-Ray's intentions are. Is he hitting on you? Why is he looking at you like you were a piece of meat, and he a hungry lion? Did you *want* this attention from this large man who breaks people in half for a living? Let that swirl around in your head for a bit and remember that this is how you can potentially come across to someone else.