You are wrong. Atheism is NOT a capital sin. There is only ONE sin that is a capital sin, and I am not going to talk about it right now.
How do I know that atheism is not a capital sin? Because there are thousands and maybe millions of people who have turned from atheism to theism. When they do that, God forgives their sin of atheism. So, how could atheism be a capital sin if it is forgiven?
Yes: tell the brothers of Moses in the Golden Calf episode.
You decide to forgive: this is your choice not G-d one.
I don't agree with your choice.
Thank You and best regards.
But you better learn to forgive, willingly, from your heart. Because if you don't forgive, your mistakes won't be forgiven, either. Rather, they will all become capital sins.