I have a question about atheists who have converted to Christianity?

Okay, this is kinda deep but it is important to me. When I was a young teenager in high school I was pretty much an atheist. I used to say things like "God doesn't exist" or "I don't believe in God". Some would consider that the sin of blasphemy. But! that obviously wasn't the case because a couple of years later I found myself to be a born again Christian. I have a fear and reverence for the things of God. In my opinion, the way I understand the Bible, the sin of Blasphemy can only be committed by one who knows God, has recieved his spirit, and then turned and cursed him. It cannot be committed by someone who doesn't even know what blasphemy is, or who God is! I think it would be a mistake to call someone a blasphemer when they don't even know what blasphemy even is truly! And they have never recieved God's spirit. God will have mercy on who he wishes to have mercy.