There's no question about it, being stared at by some retard you've never even met can be annoying. It happens to me all the time. My response is to just ignore the person. I make him invisible in my mind (it's usually him, not a her). Staring is a harmless activity, unless you allow the person staring to get inside your head. It's a form of aggression. But not all aggression needs to be countered with yet more aggression. That only leads to an exchange of words, and possibly a physical altercation. These things I don't need in my life.