her arse handed to her on a plate yesterday by 99% of the respondents for behaving so rudely
Hardly a scientific poll, is it.
And, of course, we don't judge whether behaviour is appropriate by whether a group of time-wasters on the internet don't like it.
I recognise what the OP says. I used to live in a walkable city with a large homeless population, and used to be approached with an Excuuuuuuuuse me very very often. Always in a very assertive tone which is designed to make you pay attention.
I look a bit vulnerable when I'm out and about, perhaps because of how I carry myself, or because I look a bit of a day-dreamer. I'm also the kind of person that strangers talk to on trains.
So I had to learn to interrupt with a quick 'no, sorry', being assertive back. I also have to use this now with people going from door-to-door with hardship stories. The idea you have to stop and listen patiently to anyone approaching you with an 'excuse me', just because that was good behaviour in villages in the 1950s, is frankly insane.
This doesn't mean I don't stop to help strangers in distress or whatever, or people who clearly want help with things like taking a photo or just asking, 'sorry, is this the Newcastle train?'
OP, you were fine, and I'm sorry you have to change your journey because of a creep.