I did this job for a few weeks back in 2000 
In my defence, "chugging" hadn't been around very long and I'd actually signed up to support two charities after speaking to two extremely polite and respectful chuggers who'd managed to get my attention without invading my personal space or patronising me. Because of these two positive experiences, I actually thought that this kind of direct fundraising was a brilliant idea.
As it happened, I couldn't hack it as a fundraiser because I was crap at getting money out of people. I was quite good at getting them to stop (by smiling and asking them if they had a minute to talk about Greenpeace or the NSPCC, not by blocking their path or calling out chirpy witticisms) but I was no good at continuing to hassle the person to sign up after they'd said they couldn't afford it.
And it was very difficult to force myself to keep smiling and being upbeat and friendly after hours of people being shitty or just looking through me when I spoke to them (I know, I know, they didn't ask me to speak to them in the first place). Weirdly, men would stop for me or my female colleagues but not for the males. And in the whole time I did the job, I swear that not one woman between about 19 and 50 stopped for me although they would speak to the men on my team 
Anyway, when we were being trained, we had quite a lot of instruction on how to approach people and about what wasn't acceptable behaviour. We were never, ever to stand in front of someone to stop them getting past. And obviously, walking along with someone or running backwards to stop them passing you would have fallen into that category. We were never ever to make comments like "so you don't care about the environment then" if somebody didn't stop. Same for cheeky or patronising "attention getting" comments to someone you were trying to speak to. Our trainers used the example of those pushy promotional sales people you'd sometimes get in high streets trying to sell beauty treatments/haircuts/gym memberships as what they didn't want to see from us.
Basically, the company was very strict about its fundraisers not pissing people off beyond the fact of us being there in the first place. I'm honestly shocked to hear about some of the experiences people on this thread have had with chuggers being sarcastic, overly pushy or physically blocking their escape! Presumably the training is less rigorous nowadays or maybe there are different fundraising companies in on the act, who are less scrupulous.
It's not as bad as that where I live, thankfully, although I've experienced the "hello lovely lady" patronising type of opening gambit. In this case, I stopped and told the guy he'd get nowhere by patronising women he was trying to sign up. He was apologetic and, I think, surprised. Hopefully it made him realise that his approach was alienating many people rather than charming them. Although who knows, maybe it was something that worked for him - I saw enough women being slightly giggly and coy with my male colleagues back in the day to completely dismiss the flirtation effect 
OP, (if you've read this far!) YANBU to feel the way you do. Not sure if you were unreasonable to actually shout abuse. I kind of think it's fair enough if a chugger's been openly rude to you but if they're 'just' being pushy, it's a bit OTT. I tend to just say "I'm sorry, I'm in a hurry" and just keep walking. I never ignore them completely as, at some level, I do empathise with what them doing what can be a really difficult job.