This is precisely the reason why I hate these people. And the same reason why I have no time for unsolicited calls to my front door. My wife thinks I can be a bit rude and perhaps I can be at times, but don't come to my house or try and stop me in the street and think you can intimidate or embarrass me into giving you money. Because it won't work. Now get off my property before I set the Rottweilers on your sorry behind.
And before anyone says anything, I already give money to charity; the funds are deducted from my wage every month so I know the money is going to my chosen charity. I don't give money or personal details to people in the street and if they don't like my response to their attempts at getting cash off me, they can go and jump. Preferably off a very tall building.

EDIT: And don't get me started on Jehovah's witnesses. I despise these preachers and almost as much as those annoying charity types. For a while now I have started telling Jehovah's witnesses that I worship Satan. You'd be surprised how quickly they suddenly have to be going. Good riddance.