I mean, you can talk about things like how we rejected the plan of the all powerful creator of the universe by having our ancestors eat magical fruit from a magical tree. And that we need to freely chose to follow God and thereby be given infinite reward and avoid infinite torture arranged by an all loving magical man in the sky.
And sure, even the slightest sin needs to be put right by God donning a baby suit, living a perfect life and dying as a sacrifice of himself to himself, so that we can choose to worship this or that.
If there were a God, why would there be any ambiguity as to what this God wants. Hate gays, love gays, deny them marriage rights, stone them with stones until they are dead, etc. At the very minimum any actual real God should make explicitly clear to everybody, in their own language, exactly what God wants for them, or wants them to do in whatever situation. Even if we choose to do something else.
I fully grasp that this seems wonderful to you, that God created a universe with 72,000,000,000,000,000,000,000,000 stars just so that the intelligent monkeys on this one dinky world could be saved from a system that he himself set the rules for. The idea that the universe was made for you, that the all powerful creator of the universe loves you, that you don't have to die but can live forever, and those who disagree they are tormented for all eternity. This is all stuff people would make up. It doesn't really make sense if you think about it.
It isn't too hard to go from an eye to an eye, to maybe we could not kill my uncle and instead kill some cows for your cousin and you guys could have all the meat. And then the unseen kings in the sky, equally get appeased by giving them meat. How blood propitiation arises is really straight forward. But, then to found a religion about a demigod savior who dies as a blood sacrifice of God to God (as the earlier Christian view got moved into Trinitarianism) and so you just have God dying as a sacrifice of himself. Or at the best, God saying here have my son, torture and kill him so that I can forgive you.
You say, "It seems very unlikely that these pagans and Jews would come up with religion that contradicts their instincts so radically. " But this is wrong, it doesn't it very likely that they would have come up with a religion that so profoundly conforms to their cultures. The sons and daughters of the gods and their wacky adventures, the sacrifice of a demigod as a blood sacrifice, this is exactly the religion they would have invented. Nothing about it would strike a sour chord. It's exactly what the Jews would need after the fall of the Temple. If we can no longer pay cult to God by sacrificing at the Temple, what can we do? -- And the answer is accept the once and for all sacrifice of the Messiah, who came and give victory not over the Romans but over death itself (people would have noticed if somebody killed all the Romans).?
While I do admire that you properly approach the subject with at least honesty. And I'll happily be the first to condemn folks like
A goodly number of Christians believe in God because they say they have a personal relationship with God and talk to God. And they do, or think they do. It's a pretty interesting mental trick where you confabulate what a person would say and because gods are allowed to be telepathic they accept that the god really is talking to them. People sometimes do it with aliens and with ancestors too. More commonly parents and coaches and people who boost you up or tear you down, save that those people aren't suppose to be telepathic so they must just be a fiction. But, people don't notice that the god in their heads loves and hates the same things as they do, and agrees with them at every turn, and the gods in the heads of two different people never agree with each other.
People can easily be fooled. You might even buy into that stuff you wrote about how blood sacrifice is needed by us rather than by God. But, really if you dig down in it, it really doesn't make any real sense. But, it's admittedly hard to see this if you currently believe it. So, can you at the very least see why I think it doesn't make any sense. Why I think that this is what cultures would have invented. After all, we all agree that of the thousands upon thousands of religions out there the vast majority of them are false. But, I cannot actually see any difference between those religions and your religion. What criteria could I use to determine that Islam or Juju up the Mountain is false but your religion is true? The vikings invented a religion where you go to heaven basically if you die being a really good viking. How very predictably convenient!? If I'm right then a bunch of demi-god loving pagans and a bunch of blood sacrificing messiah worshiping Jews would have invented a demigod messiah who dies as a blood sacrifice so that all the people who believe this story go to heaven and all of those who don't burn forever in hell. Isn't this how a chain letter works, the important bit is passing it along, not being a good person. Gandhi could have lived longer and done more than he did in his life, and he still would have died a Hindi, and not taken the only path to the Father which is through the Son.
The idea of "rubbing somebody's nose" in their wrongness is repugnant to me. It's taken me years to cultivate a love of being wrong. To find those times I am wrong, quickly accept them and admit them publicly because really that's the only way we grow. When we think about being wrong, we think about the pain and the shame and the embarrassment, but that's how we feel when we realize we were wrong. And attacking people there or making that harder is absolutely repugnant. Being wrong, feels exactly like being right, so long as we don't realize the error of our ways. So any hurdle or attempt to compound that is the pinnacle of assholedom.