Before I say anything, I'd like to say that convincing other people to become atheist is really hard. Really hard. I wish you the best of luck if you want to go through with it.

I think that if someone isn't already atheist, explaining to them why they should be will need to cover a lot of ground before its likely to work, and will probably need to be really long.

You never know until you correct a previously false belief. If you care about anything, you should try and hold only true beliefs, because one false belief can be enough to destroy what you hold dear.

This conclusion isn't obvious to non-LW readers, so you should try unpacking your thinking a little bit. I think you should stick a real life example in here to make it more tangible, ideas like this tend to be glossed over when read casually.

one false belief can be enough to destroy what you hold dear.

Many people hold beliefs dear.

If someone proposes you to adopt one, do not drink that cup, it's poisoned.

If you have any advice about how to detect flaws in reading, tell them how. Most people would that they shouldn't adopt obviously fallacious modes of thought, but most don't know that they have cognitive biases built-in.

Note that all three answers share a common structure.

Most people will not leap to probability from this.

Also, it might help to make it clearer that "I don't know" means that you spread out your probability.

There is hope however: if we are both reasonable, don't have flaws in our reasoning, have roughly equal access to evidence, and honestly attempt to reach the truth together, then we will eventually agree. At least one of us will radically change his mind.

Let's say that halfway through such a quest, you are still 99.999% confident the Earth is spherical, but I am only 60% confident. It means two things:

I changed my mind. We still disagree. This time, the disagreament is not as srong, but still significant: you estimate that flat Earth is barely worth considering. I on the other hand, think sailing West means 40% chances of falling at the edge of the world, which is just too risky.

This sweeps all of the math behind Aumann's Agreement Theorem under the carpet, and does so before people are convinced of the whole probability as belief point.

Also, there are very many visceral reasons that someone disagreeing with you feels like they're attacking you which you don't address.

Other notes:

I'd suggest that you talk about what constitutes proper evidence for a belief. Almost every religious person I know insists that something in their life shows them that God exists. I suggest mentioning (and explaining) belief in belief.

I hope that helps.