You are trying to put your values on someone else. It's a very misguided and closeminded way of thinking.

Being atheist means nothing more than not accepting the claims of god(s).

Buddhists are inherently atheistic, but believe in reincarnation.

I am an atheist myself, and know that whether I'm good or evil in my finite existence will not effect my infinite nonexistence. I can be a civil paragon, a criminal, or a lazy bum. Doesn't matter. I do know that I will cease to exist like everything else. So, I make the best of my limited time at hand.

Basically, you can't comprehend what someone else thinks. Don't assume.