Most of the world probably does believe this, which is something I find profoundly disturbing. We have a long way to go as a species in developing a sane ethics system.

However, considering the progress we've already made, I have hope that we can make more.

Perhaps ethics is not something absolute, and is a game thorethic optimal strategy that changes as the rules of the game change.

If hunting is the only thing you can do sane ethics system would allow killing the whale no matter how intelligent creature it is. And letting members of another tribe die instead of trying to share and risking members of your own tribe to die is a sane thing too.

But things change if you a member of a civilization that can produce as much food as it wants without killing anyone.

My understanding is that most (many?) vegans even today accept killing when it's necessary for survival. That necessity is just extremely rare for modern humans (or it should be, in a fairer world).

That said, I find the idea of game-theory as a "universal basis" of ethics intriguing.