See: First amendment
Perhaps if women conducted themselves with a certain amount of class then it would actually be reasonable to take their side in such issues.
They want pleasure
It’s about respect. There are ways to conduct yourself as a gentleman and still offer your compliments to the ladies. You know smile, or wink, or just be yourself, and tell her how nice she looks, but to actually ‘harass’ someone means you are making them feel uncomfortable, and I don’t think you would like feeling that way, sir. I highly doubt anyone would object to that.
Because it’s usually rude. Just because it’s legal doesn’t mean it’s ok.