Western civilaization is based in Christianity, these people are Christian in many ways even if they claim to be atheists. Like one atheists I was arguing with who got really upset that the pope had lied ( it was something like that). So asked him if he didn't believe in God why he had such a problem with lying. So he says a lot of religions have rules against lying, but who cares, there is no God you can do whatever you want. But they don't want that either, they want God's rules, some of them anyway.
Point is, these people aren't really atheists, at least their behavior and worldview is not consistent with the belief that there is no God. They are kinda more like heretics, a lot of them anyway.
Imagine if you really honestly believed there was no God.