Well, there are people who masturbate in public places, in a harassing way. I haven't seen women doing this. It's usually done by men. Sick people. I see more of this word ‘wanker’ related to that group.
It's a pity that people are so prudish about masturbation, it's something necessary to get to know each other, especially women. Many of them, because they don't know themselves at all, have horrible experiences with their partners afterwards. And they don't know how to get pleasure.
In public places? I wonder if that's unique to your area or it's widespread? It's not something that happens here, certainly not that I'm aware of anyway. I think there's public indecency laws against that sort of behaviour.
As for the rest, yep I agree.
Oh yes, it has happened to me while walking in my neighbourhood. It's really scary. Law? Yes, I suppose there are, but imagine it's unknown men lurking around, waiting for a woman to walk by and touch themselves and show... you know. It's really scary if you're alone. I've decided to avoid those places where they hang out and I don't walk there. And I don't walk there alone.