I've read many, but not all of the posts. Its nice to see what other reasonable people think. It helps me coallesce my own thoughts. That being said: If an attactive woman is in public, there is nothing wrong when a man looks or even stares. After all, many women go out of their way to enhance or emphasize their attractiveness. (Perhaps that is why they call it "attractive.") They do so partly to attract attention. Some even do it in hopes of attracting a potential husband. Thus, there is nothing wrong with looking. I have trouble saying there is something wrong with someone putting themself in a normal position, in a public place, from which they can look. (Think of how at thinggs like the Acadamy Awards spectators wants to be as close to the red carpet as possible.) Even if the one doing the looking is "creepy" he has as much right to look or stare as anyone else. SO LONG AS ALL HE DOES IS LOOK. If you have a bad feeling about him, I think a friendly greeting which lets him know you have noticed him noticing her will probably suffice to keep him in line.
At the same time, putting himself into an unnatural position or location that enables him to watch warrants more action. Likewise, putting himself into a position to unnaturally invade her privacy, e.g. mirrors, telescopes, or cameras held below skirt level and pointing up, also warrant more action.
