I don't think they secretly believe. I believe that they disbelieve.
But, an atheist could never empirically prove to me that they are an atheist. It's just something we have to take on faith.
Sounds like a word game to me. Or else you have a bad idea of what atheism means.
So, if an atheist were to tell me, "Only empirically proven things exist," then I would have to assume that atheists do not exist because I can't empirically prove that they are an atheist in the first place.
Atheists are not stupid enough to think that only things which have been empirically proven to exist can exist. The universe is so large that there will always be many things that we can't empirically prove yet still exist. For that matter, atheists are also not stupid enough to think that subjective things (preferences, tastes, etc) can be proven empirically to begin with. You can't 'prove' that I like chocolate, or that I like peanut butter - you can only judge it based on my reactions to those foods.
However, a subjective belief can never prove that something objective exists. Which is the problem, since most religious believers think their subjective belief reflects objective reality.
The sacrifice was his torment. He was tormented very badly.
According to the Bible. However, the Bible doesn't prove that it actually happened. It only shows that someone wrote about it happening - there's no objective evidence to prove that this torment ever actually happened (never mind the whole resurrection business). All you have is your own subjective belief about what's written in the Bible. But you can't prove that your belief is objectively true, anymore than someone else can prove that it's objectively false.
Animals are not making a choice to do that. That is how they were made. It is not murder when an animal does it. Only humans can murder. God can not murder either. It is only something humans can do. God just takes his children. It is not murder.
What, you think animals do not have volition? You think animals don't make choices? You think animals don't have morality of their own? Maybe you should spend some time checking out recent animal research which indicates that animals do have morality (admittedly, a primitive form of morality) and that they do make choices.
We also see some kinds of animals exile members of their social group that act too viciously towards other members of that group (and kill them if they don't take the hint), which is a clear mirror of human tribal/social behavior. Indeed, humans do exactly that, both long ago and today - if you act in a way that unnecessarily hurts other people of your social group, you're exiled from that group, or killed if you try to stick around.
Instead of reciting platitudes about how animals don't murder, you might want to spend some time thinking about the fact that even today, we have a large number of people who don't think of other humans as actual people. For them, killing a "non-person" human is no more an act of murder than killing a dog or a horse would be. And then you might want to think about the fact that the Old Testament treats most humans as non-persons, and thus whether it was the Hebrews or YHWH who killed these "non-people", it wasn't murder because their victims weren't actual people (according to them). For that matter, it happened long after the New Testament was written - take the way dark-skinned humans were treated for hundreds of years. They weren't actually considered people either, which is why they could be bought and sold as property, separated from their families, beaten, raped, and even killed by their masters with near-impunity.
In the same way the blood of the lamb (Jesus) keeps Yahweh from sending us to Hell.
Except it doesn't. If it did, nobody in any religion would be threatened with Hell. Yet there are plenty of Christian sects which state, unequivocally, that if you don't follow their particular rules (usually far above and beyond simply accepting the necessity of the "human sacrifice"), you're going to hell. So no, it doesn't keep anyone from going to Hell.
With all due respect, I know the Bible very well. Christians are the ones who know the Bible. Taking advice on the Bible from an atheist doesn't make sense to me.
I seriously doubt you know it half as well as you think you do. I wouldn't be surprised if you didn't know it a tenth as well as you think you do. And that's because the vast majority of Christians don't actually read the Bible. They just open it up when instructed to by a religious leader and read a few passages, then close it up until the next time they're told to open it. And while not everyone is like that, most Christians who read the Bible on their own just focus on the New Testament, specifically Genesis, Exodus, the Gospels, and Acts, and cherry-pick the rest as needed. So don't try to tell me that you know the Bible very well, because the odds are very much against you knowing very much about it at all.
Have you actually read the entire Bible, cover to cover? Have you studied and seriously thought about everything written in it? If the answer to either of those questions is no, you don't know the Bible all that well.
For example, if I wanted to know what Muslims believe, I'm gonna ask a Muslim, not a Jew.
Many atheists, at least in this country, are former Christians who started seriously reading the Bible (and I mean the whole Bible, not just a handful of books within it) when their faith wavered. So you shouldn't dismiss their knowledge of the Bible just because you don't agree with the conclusions they ultimately came to, especially given the extremely high likelihood that you are much less familiar with the Bible than you think you are.