So maybe killing other human beings in the name of religion is bad, but at least people can defend themselves, I came across, "Dogs in Islam", which says, "Last Ramadaan, I wrote an article highlighting the phenomenon whereby misinformed Muslims took their dogs (and/or cats) to the animal hospitals or mobile clinics during Ramadaan, to have them put to death by lethal injection. The reason given by the majority of these Muslims was that Islam forbids them to keep a dog."
"Healthy, happy animals belonging to Muslims are also brought in to be put to death. This is a very disturbing and un-Islamic action..."
Not that Christians are much better, the most famous being Descartes and his views that animals can't feel pain. His views were used to justify cruel experiments that were performed on animals. At the same time he is said to have had a pet dog that he appreciated, I always thought "Descartes' Dog" would be a good title for a book.
Dog's saliva has a bactericidal effect on E. coli and S. canis, whereas cat saliva can cause Cat-Scratch Disease. Of course, they both eat rather suspect things and don't brush their teeth so it's not all good.
Also, dogs and cats can make their own vitamin C. Does that show a bias or just a cunning plan? The point of my initial Googling was to work out why my dog's food had all kinds of ingredients but not vitamin C. I came across these other interesting facts in the process.