I look at ethics from different perspective. If I see that a petitioner (merc, monster slayer, dancer, scholar or some such) has a wife or husband in my fort, I allow him or her even if I have population high enough. Also if this is an old widow looking for work I allow too, especially if close to death.
I see no ethical difference between dogs, cats and pigs, except cats are most annoying and dogs and other war-trainable animals are best used in the field. Fortunately cats have natural explorer abilities, so I throw a pair of them into caverns to explore, and replace when necessary. As for war-trainable animals, they are uncaged after becoming adults. This is a difference to other animals, which are caged after birth (unless grazers), and only several of them are kept outside.
By the way, despite using war animals, thanks to using trained military I don't really have much injuries amongst anyone. My war dog is more likely to die from old age than from battle wounds. Every year some of the dogs die of old age (I have 70 dogs at the moment), while rarely is one injured or killed in combat. I don't count dogs chained and used as bait (along with cats) outside, but even they are quite safe, once I've built drawbridge curtains around every chain area.
As for nobles, they don't act as true nobles (fortunately), so I'm nice to them. I do not have justice system, but they don't grumble. You have as noble nobles as you deserve (read: let them).