At the more serious end of the harassment scale are assault and rape. Sometimes a pleasant comment is followed by a hostile one. Women may fear that minor harassment is the first step towards a more serious attack. Women deserve to be able to go about their business just like men. Public spaces should be for everyone without discrimination.
Public harassment has serious adverse effects on some women.
If women are worried about harassment, they can become suspicious of innocent gestures and hostile even towards non-harassing men. Learn about the problem so that you become more sensitive to what might offend others. Don't cooperate with groups of men who harass. Act to frustrate or oppose harassment. If a woman doesn't respond, almost certainly she didn't welcome the comment.