I may be putting words in their mouths as they often do for us, but PETA is very anti breeders and in a world with only spayed/neutered "companion animals" they die out pretty quick. If you read PETA's stance on keeping pets you can see how they think keeping domestic pets is cruel. http://www.peta.org/about/why-peta/pets.aspx
I don't have a link from HSUS handy, but I have seen some very negative quotes floating around from the CEO of HSUS.