I've been an atheist for 50 years now. I was raised as a Catholic and the turning point for me came when I encountered the teaching that Jesus was physically lifted up into the sky 40 days after his resurrection. I asked the nuns "Why don't we get into a spaceship and follow him up there?" and that was the beginning of the end. A few years later, in high school, I shocked my friends by confiding my conclusion that man is "just a pile of chemicals".
I have some points I'd like to raise, but I'll post them in the appropriate categories.