When a human kills an animal for food, the human does not pay for the crime of killing that animal. But when a human kills another human; there is are arrests, forensic investigations, court drama, imprisonment, and even death penalty. What makes mankind so important and animals so disposable? Why are animals denied from justice? Why does a human feels the need to bleed an animal for food when he/she can survive on plants? For the religious lot: In the eyes of God, all beings are equals. He loves each one of them equally. So by this logic, he cherishes each life equally. For God, a human who has killed seven innocent humans is as guilty as a human child who has killed seven birds for thrill. Then why are crimes against animals not the same as crimes against humans?

It's perfectly reasonable to ask moral questions about killing animals. It's not a trivial issue. But it's also perfectly reasonable to ask whether all animals are morally equal. You say that in the eyes of God, all being are equal. But even taking it as given that there's a God, I don't see much reason to believe that. And in any case, trying to sort out what God might think about things is a slippery route to moral conclusions. What matters isn't what God's conclusions might be; what matters are the reasons.

In many cultures, it's common to eat insects—ants, for example. Do we really think that killing an ant and killing a human being are morally on the same level? It's not obvious that they are. Ants are alive; there's no doubt of that. But so are bacteria. So are lettuce plants. We don't think that it's wrong to kill something simply because it's alive, and so among living things there must be distinctions—features of the living beings that make it more or less wrong, or even not wrong at all to kill them.

That's where at least part of the answer to your question will come from. Just what the right distinctions are is controversial. It's a matter that reasonable people can disagree about. But it's where you should look. There are many differences between, say, a cow and a human. Both can feel pain, and that's important. But cows, as far as we know, aren't self-conscious, don't have a self-concept, don't have the capacity to have plans for their future, don't have hopes, don't have dreams... Maybe that's not enough to show that it's okay to kill them for food; I'm not offering a view on that question. But these are the kinds of considerations some people see as relevant. More broadly: the more cognitively primitive a creature is and is destined to be, the more we're inclined to think that it doesn't get the same moral consideration as humans or intelligent animals of other sorts.

You might reply that this gets us into tricky territory and you'd be right. After all, some humans are profoundly cognitively disabled. Is the point that they get less moral consideration? That's a good and important question and I'm not suggesting that the answer is yes. But if the answer we come up with leads to the conclusion that it's wrong to kill mosquitoes, then it's worth worrying that something has gone wrong with the reasoning.

We should think hard about our attitudes toward animals. We should also think hard about our attitudes toward unborn fetuses, and about our attitudes toward the profoundly intellectually disabled. And we should be leery of glib answers. But it's hard to believe that good answers won't rest on making distinctions and thinking carefully about the larger context in which the questions come up. Doing that work is what your question calls for.