I don't think people realize the extreme lengths the group has gone through in the past to discriminate against gay people (see here and here and here and here and here). It's a HUGE issue for them. So when you drop money into their bucket, you are funding an attempt by a religious group to get involved in anti-gay politics in the US.
I made up a card I will hand to the next bell-ringer I hear. I will look them in the eye and say, "Why do you hate me? You're an asshole."
Download a PDF file you can print out for yourself (10 cards per sheet, or use Avery-brand perforated business card in styles 5871, 8371, or 8871):
Front of card (http://www.patrickkellogg.com/stopringingthatdamnbell/Front.pdf)
Back of card (http://www.patrickkellogg.com/stopringingthatdamnbell/Back.pdf)