Hi Rachel.
One thing worth saying from the get go, in response to this from you:
Instead, I've seen many atheists who live very healthy, prosperous and happy lives and they obviously don't believe in keeping God's commandments.
Whilst atheists, by definition don't believe in any divinely ordained commandments, the vast majority believe in living decent, moral and honorable lives. The mileage will vary a little from person to person, when it comes to where lines are drawn, but when it comes to biggies like not killing someone, that's something that pretty much everyone, atheists and believers, all agree on.
Your quotation isn't entirely clear on the point, but if you think atheists lack morality, simply because they don't believe in a divinely ordained code, then I am afraid you're wrong.
Could there be any greater conceit, than for someone to believe that the universe has to be simple enough for them to be able to understand it ?