I think you're raising two different issues here. One concerns our relationship, political or moral, to all other sentient beings, human or not. This is an issue of considerable passionate dispute going back several thousand years, and is by no means as settled as you seem to believe. The other issue is how we should deal with other human beings. Human beings are different from other animals in that they have much more power; they can make war on us and kill us, whereas other animals are for all practical purposes utterly helpless. I am not going to attempt to deal with our relationships with our little furry brethren here because I don't think, based on past experience, that it will work out well.
In the case of dealing with other human beings, if one has a choice between constructing a community in which some must live and others must suffer and die, and one in which everyone has some sort of chance to live, and one chooses the former, one has in effect chosen war, a class system, and slavery, because this is the only way such a situation can persist. I would think this would be obvious: human beings do not voluntarily accept subjugation and death and have to be continuously trained and disciplined using force, threats of force and fraud to do so. We can call this sort of arrangement "the State". Those who do the training must be constantly on their guard lest the system be overturned and they find themselves on the other side of the gun or lash or whatever it is they use. So they are not much freer than their victims.
There is an additional problem with the State: technological advances, or "progress". As more and more power becomes available to human beings, the methods and devices which they use in combat with one another will become increasingly destructive. It seems inevitable that some configuration of such methods, devices and events must occur sooner or later which will destroy the community physically.
You'll notice that I have rigorously avoided sensitive stuff like morals and aesthetics here. There's no idealism, altruism or communitarianism. My arguments depend entirely on my assumption of a preference on your part for personal freedom and well-being. Of course you may disdain these things as well; there are those who do.