I'm not saying it is the same.
It's just that our reactions to the cognitive dissonance are the same.
For example, you had attempts at laws of humane handling of slaves during the US slavery period. Slaves were disposable creatures, just like animals.
Our handling of the cognitive dissonance was attributing inferior characteristics to slaves (intelligence, different skin, can't learn to read etc.). Same thing is done with animals to argument their handling and disposability.
Then you try to add "humane" into your reasoning. Which is filled with oxymoron terms like "humane slaughter", "humane rape", "humane electrocution".
Justification of having the right to a slave's life because you feed him and give him the right to live is absolutely mirrored in the argumentation when it comes to non-human animals.
Nice thought experiment to confirm your cognitive dissonance is to think of what you would do with homo neanderthals or homo erectus or maybe australopithecus genus? Would you keep them in zoos? Have them as disposable servants? Of course you wouldn't.
Cognitive dissonance is present because you've been raised in a certain environment that starts to have (or you start to recognize it having) characteristics that go against your moral stands.
If you try to have thought experiments similar to the one above (the environment in which you didn't grow) you can think more in line with your true positions, and leave the faulty argumentation behind.
Of course, you might try to skew the argumentation for the homo/australopithecus case to be consistent with your actions in your non-human animals case, but that wouldn't come natural, that would come through cognitive dissonance (you spot the connection between the two, it distrubs you, and instead of admitting that environment conditioned you - cognitive dissonance comes to play).
Slavery, nationalism, fascism, heterosexual supremacy, male dominance, all are ideologies spawned from existing environments whose supporters suffer from cognitive dissonance. All of these ideologies share the same characteristics as those of enslaving animals, massively killing them, poisoning the environment etc. In that particular way, these ideologies are the same.