I do generally agree about not jumping to the worst conclusion and acting as if someone is a criminal in situations like these. But, I don't think that's what the OP was doing here. Had she used a panic whistle, called the cops, or started screaming at him, then yes, all those would be overreactions. But just plain not wanting to engage with him and being abrupt, I don't think is rude. When you approach a stranger on the street and make a personal comment to her you really shouldn't be surprised if they aren't friendly.
I agree that sometimes here we are too quick to jump to 'evil intent', and am often the first one to think people call out someone as being 'a safety issue' too quickly. This wasn't a safety issue, this was an annoying guy, and the OP reacted accordingly.