I have a lot of debates with religious people, and I’m always amazed by the same thing: the complete lack of any idea of how to talk to someone who doesn’t believe what you do.
There is almost never any rational discussion of “This is why I believe the things I believe”. The theist’s beliefs are simply presented as fact, as if I had never heard of Christianity or Islam or Cargo Cults or whatever. It’s quite baffling.
I’ve tried to point this out many times, and it’s usually met with either “But my beliefs are true!” or ignored. It’s a pretty serious failure of critical thinking.
It’s very odd to me that people respond this way. When I am arguing with a theist, I don’t just keep repeating “There is no God” because it wouldn’t make any sense to do that. Obviously, the theist already knows that I don’t believe in God, and obviously, they disagree. I do see atheists doing that sometimes, but I don’t think it makes them look very bright.
It is the mark of an educated mind to be able to entertain a thought without accepting it. – Aristotle
If someone told me they didn’t believe 2+2 was 4, I wouldn’t repeat over and over that it was. I would demonstrate it. This is pretty easy to do with things that are objectively true. Of course, it’s impossible to demonstrate that God exists, so that isn’t an option for the theist, but what a hypothetical rational theist would do is present reasons why they believe what they believe.
The way to have a discussion with someone who disagrees with you is to start from the common ground of things you agree on, and try to build a case for your idea based on those. If you can’t figure that out, then you probably shouldn’t be trying to argue your ideas with grown ups.