From this position, I derive that behavior towards animals should be the same as behavior towards humans with reduced or differing capacities. That it is almost universally not the case appears to me to be evidence of the limits of the capacities of many humans to transcend a brutal complacency rooted in a hideous egotism.
I know this, as opposed to believe it, from observation. I have been around animals all my life, currently live with seven of them, and I have lived with as many as twenty one. I have spent my entire life observing them and comparing their visible behaviours and moods with those of the human beings I have known.
Those behaviours are all there in various forms. Further, animals learn in a self motivated manner. We currently have a cat that will turn a doorknob to open a door. He flushes the toilet. He wipes off the mirror to see your reflection. His name is Smitty, and he's quite a character.
I am convinced that the general attitude that people take towards animals is caused by the same major character flaw that causes them to follow religions - they are unable to contemplate the fact that people are no more special than they make themselves, and that the universe isn't a cradle especially designed for human beings. How sad for them, and for the animals we share the universe with.