Razib Khan thought the phrase "humanitarian treatment of animals" is better, because "rights" implies a lot of other philosophical assumptions, and I think this is a useful clarification. We might want to treat animals in as pain-free, discomfort-free way as possible, even if they have no rights in a formal sense. We could still use them for whatever purpose we deem necessary but be scrupulous about it, simply because it is good for us at some level - spiritual, emotional, cultural - to do so. CS Lewis was against* what used to be called vivisection.
I recently heard an intelligent person make a solid pitch for eliminating animal cruelty. He correctly notes that it has wide support in both parties, with the forces against the idea coming sometimes from the left, sometimes the right, but most often from food industries that give money to both parties, but always more to those in power, in what is a purely practical decision. Yet as with many things, targeted protest and pressure are more powerful in politics than majority support. Zell Miller recounts that an older politician warned him as he was coming up "Two-thirds of the people support allowing gambling. But that one-third will defeat you."
Nonetheless, he made one set of arguments that I think is just backwards. He claimed that we have to be taught to be callous and ignore cruelty, that we more naturally want to be kind to animals. "If you talk about it with children, they just naturally are against it. Parents know that there is a time when the child becomes aware that what they are eating is an animal and they don't want to eat those things anymore. They have to be made to. This is true everywhere." (He does not have children.)
He didn't grow up in my neighborhood. Playing baseball with frogs was considered a hoot, and playing practical jokes on cats was a source of humor. As for "everywhere," my sons from the Transylvanian village were very quickly shamed that the amusement they took in teasing animals cruelly was not acceptable. If the argument is that in modern Western middle-class society children are now horrified by animal cruelty I think he has a point. But this is because they have been propagandised that woodland creatures can talk and giggle and have rich family lives. Even fish have personalities on Disney. Cute animals dominate children's picture books. Secondly, they do not encounter food animals very often anymore. At most a chicken or goat used for eggs or milk, and not turned into food themselves. The animals they know are pets, and they have evolved to be attractive to humans to get better treatment. Even then, not that great in all societies.
So that is not what children "naturally" think, it's what they already think by the time they get far enough along to discuss such things with adults.
*Interesting site, now that I have come upon it.