In my experience there are two types of people who would consider themselves atheists.
A majority of the atheists I know would state that there is no evidence of any god or deity having any effect on our universe or in our lives, so there is no need for religion or spiritual belief. Religion, for better or worse, is a human institution that can have an impact on culture, morals, philosophy; in fact I know quite a few atheists who are interested in theology purely as an academic exercise. According to this first group it's cool if you decide to hold to a religious belief, just please don't let your beliefs have a negative impact on my life.
Then there's a small group of very vocal atheists who might be better described as "anti-theist" - the ones who define themselves based on their opposition to a straw-man version of organized religion, respond to any slight display of religious belief with snide and judgmental comments, send their kids to "evolution camp" where they spend the week tearing apart religious texts because, well, this passage is unclear about whether Moses went to Sinai or Horeb, so obviously the whole thing is nothing but lies - even the parts that could give insight into human nature or ethics, and who make it clear that they view anyone who holds to any form of religion as delusional or even downright ignorant.
In my experience members of the second group can be quite dogmatic, even more so than most religious people I know. The statement "There is no evidence that any god exists or has any impact on our universe" is VERY different from the statement "God does not exist."