Excuse me miss…

Hi! Hello There! Got a sec? I just wanted to talk to you about whalehunting/climate change/cancer/wariniraq/gaymarriage/childhunger - insert worthy cause here. Its the classic form of (legal) street solicitation. Abnormally happy people in bright shirts catch your eye, beg you to stop, and then deliver a heartstring-pulling spiel which inevitably has you thinking ‘Yes, I probably can afford that $30 per month. Its a good cause!”
Having done the hard-sell for charity (by phone, not on the street) myself; I’m always sympathetic. Its an awful job. People, I discovered, are rude.
Unfortunately, this same sympathy makes me an easy target for the charity-hawker. After many such encounters, I’ve built up my defences. I like the ones that begin with “How are you?” By the time you’ve said “good thanks”, you can be several paces ahead and they’ve lost the opportunity to keep talking. Today I got a “High five!!!”. That was easy. I can slap someone’s hand WHILST walking away.
The approach I struggle with is the question:
Do you support gay marriage? Well, yes, but I don’t really have time to stop.
Do you care that their are children starving in Africa? Well, yes, but I already give to a child fund.
Do you want to stop war in Iraq? Well, yes, but how is me giving you money going to achieve that?
If you say yes, you’re stuck in conversation. If you say no, you come across as a jerk. Its a catch-22 of guilt-tripping.
My latest tactic is to smile and say “I’m sorry”. I hope it conveys that I am both sorry that there are starving children in Africa, and sorry I don’t have time to stop.
For the well-paid but much abused charity hawker, I’m sure it doesn’t count for much.
What is the perfect brush-off?