Joe, you're right in regards to organizations like PeTA.
Sometimes, though, I do my best to follow charities' privacy rules, and I still get junk mail. I may not know who gave the junk-mailers my info. Only if I couldn't get their attention another way--polite letters and calls asking to be removed from their list(s)--do I send their stuff back to them.
Q: How many poets does it take to change a light bulb? A: 1001...one to change the bulb, 1000 to say it's already been done.