Until we are compassionate to all beings, including ourselves, we are doomed to repeat the lines 'lest we forget', 'stop racism', 'equality for women', 'keep our ancient forests', 'reduce reuse recycle', 'do not eat our friends', 'rats have righton', and so on so forth.
Some are under the impression that they are superior somehow. This is apparently a justification for the presumed dominance and ill treatment of others. It has been suggested that some are more intellectual, can reason better, can control and manipulate their environment. My question would be to what end? Ultimately, whatever we do to our environment, we do to ourselves.
Same could be said for oppression. With the various forms such as the African slave trade to the Americas, women's lack of equality, the treatment of the Jews under the Nazi government, the cutting down of old growths, the destruction of eco-systems, the experimentation on chimps and rats, the eating of cows and chickens, there always has to be an oppressor and the oppressed. For you cannot beat and abuse another being if you are able to acknowledge their capacity to suffer.
However, if they weren't up to your standards, if they weren't rational, if they didn't feel pain the same way you did, if they were 'heathens' or 'barbaric' and if you could go so far as to objectify them, then heck, get out the whips and let's reap the rewards in gold and silver.
Greed seems the common theme, be it the slave owner getting hard labor from his slaves, men not sharing their position and privileges in society, Hitler confiscating Jewish property, lumber magnates doing as they please with our forests, industry heads getting away with using water bodies as garbage dumps, the factory farmers being able to butcher their 'property', or researchers justifying the use of their grants.
It's hard to give up unless we know what it's really costing us. History shows we repeat atrocities and injustices over and over. There is a phrase that goes 'if we forget our history we are destined to repeat it' and Bruce Cockburn put in another way "Why does history take such a long, long time?"
Perhaps we never learned that the lesson was not just that racism, sexism, or speciesism are unjust, but oppression itself against any individual is intolerable.