The way humans treat animals is the same as how animals treat animals because humans are animals. Just because we are smarter doesn't make us any less a part of the natural world.
A dolphin is smarter than a mackerel, it doesn't make the dolphin immoral for eating them.
Is that better? Assuming they committed the crimes they were convicted for they are agreeing to avoid the consequences of immoral acts by agreeing to perform more immoral acts?
I mean, animals take active steps to stop humans eating them too. We even have laws to protect species of animals that have killed humans. Tiger hunting, as an example, is illegal.
Honestly, we're much nicer to animals than animals are to us or they are to other animals.
But you've yet to establish eating other animals as morally wrong.