To stick up for these people, it is their choice, whether it be a medical condition that causes these people to respond this way, or just eccentricities, we should not be judging them.
If someone sells a bird, I do agree, it is the buyers choice, but... some folks cannot stand the thought of their critters meet a poor end. Also, there are many people that keep animals way past their time instead of choosing euthanasia, bless them, I can't, I believe in not allowing a critter suffer- chicken, cow, horse, dog, cat, we all have our kinship with our pets.
I have a family member that cannot handle watching movies where animals are hurt, fully aware that even cartoons are not real, but cannot bear the thought of mowing the lawn from the insects and frogs that are living there.
So either way, live and let live guys. Topics like this tend to hurt feelings of those that are as they are with their animals. Be Kind.