Cheetahs are pacifists, and it's simply because they are too weak to compete with the other predators on the african plains.
Thats what pacifism is, thats where the behaviour comes from, it's a survival strategy so organisms could live on despite being muscled out of the fruits of their own hard work.
At it's essence, pacifism is a tactic for the inferior.
Weak people decided to glamorize it so they wouldn't feel ashamed.
I can see being proud of it if you're a cunning old man on his last legs, scraping through and defying the reaper on sneaky snakey pacifism tactics.
But conceding to pacifism from the get go can't be good for one's sense of self worth.
Thats what pacifism is to me and the universe. You're free to have your own little personal definition if denial will help you ward off the nagging depression waiting to pounce on your vulnerable soul.