Well bagpuss you have the legal right to put your dog to sleep but you may not do so for the purpose of feeding him to the public (in the US etc.).

You may not understand that a mature dog is more conscious and aware of the world than an unborn human but I suspect they are.

What is at work here are cultural factors that people choose out of a necessity for the pursuit of a better life. Selfish? Perhaps but few organisms (perhaps none) have no defenses or predation that does not affect other organisms in some less than holpful way.

One standard may not fit all but there are people who will always fight for the chance to impose their standards on others.

Should these people succeed they are not unlike a super virus.