I think I do answered your question but maybe it was too implicit, so let me be more explicit. A human should have moral responsibility towards non-humans because of empathy and recognizing the fact that other animals are alive as well.
Bacteria are alive too, and I'm going to guess you don't claim we have a moral responsibility to them. And as I said, humans can feel empathy for things that are not alive. The capacity to feel empathy rests entirely on the empathizer, and has nothing to do with any intrinsic properties of the empathizee. Is a psychopathic murderer morally in the right because he doesn't feel any empathy for his victims?
Bacteria are alive too, and I'm going to guess you don't claim we have a moral responsibility to them. And as I said, humans can feel empathy for things that are not alive. The capacity to feel empathy rests entirely on the empathizer, and has nothing to do with any intrinsic properties of the empathizee. Is a psychopathic murderer morally in the right because he doesn't feel any empathy for his victims?