Evidence for atheism

[Tonus]

But in sum, and allow me the analogy, God is like an unicorn: it could exist, it's viable, it'd be very reasonable to exist.

If we are considering the possibility that there exists a breed of animals that are essentially horses with a single horn in their foreheads, I agree that such a thing is plausible. As you note, we know that there are animals with horns and tusks and similar growths, so it wouldn't be a fantastic thing for there to be such an animal. A being that is anything like the gods that are often described by believers today has no parallel, nor anything that we can compare it to and say "with just a few changes, this would be a god."

We also have to keep in mind the significance of such a discovery. Finding unicorns would be pretty neat, but not outside the realm of reality. We could reasonably expect to discover them at some point, if they're really out there. Finding god would be a world-changing discovery for every person on the planet, and it doesn't seem like the kind of thing we could easily brush aside. The lack of any sign of god outside of emotional appeals and philosophical blabbering strikes me as much more significant than the idea that the universe is so amazing that someone had to have made it.