Blimey, when I asked a question when I gave a fiver to the guy that was collecting for cancer research, I can assure you that he didn't talk to me like that.
If that's the way you treat your donors maybe it's time for a change.
I have to be honest and say that if my sister had offered me a bike worth the same as I was going to raise by using it I'd have asked her to donate it direct and save me the aggro.
But then again I guess I wouldn't have got the attention.