Penn & Teller exposed this kind of stuff on Bullshit about 10 years ago. It was pretty funny. They had PETA acting like a a bunch of fucking psychos and protesting a shelter for having to euthanize animals they couldn't adopt out, and then they revealed that PETA kills most of the animals it "saves". The PETA statement was something to the effect of, "Well... yeah. We try to adopt out as many animals as we can, but of course we can't adopt them all out and some times the kindest thing to do is give them a painless death." Derp!
Kill shelters are bad, but PETA kill shelters are good even though they kill their animals at a much, much higher rate than anyone else because those animals are being killed by people who care!