Well, choosing an arbitrary ethical system because it happens to jive with your own selfish aims, for all intents and purposes that’s basically the same as having no ethical system at all. This is why you get the analogies to things like human slavery, because the same logic was used to arbitrary exclude some from consideration (e.g., supposedly biblically-founded theories that purported to show black people were on a lower plane of existence than white people as ordained by a god). Again, we don’t even apply these sort of arbitrary criteria to humans (a person who’s in a coma with no end in sight, a person with a severe learning disability…). It’s just rolling the dice and creating some arbitrarily high criteria for deciding animals don’t deserve rights.