I disagree, especially when we are talking about limited-government conservatism. Religious conservatives like to grow government in order to enforce their view of morality, while the liberal religious like to grow government in order to do the Lord's work in helping everybody out (welfare, etc.).
Being an atheist doesn't provide any atheist-specific motivation. There's no natural match because there's no specific ideology that atheists share. Marxists need to be atheists because Marxism can't have any power higher than the state. This is true for any totalitarian government (Marxist or not) that doesn't claim legitimacy from the god of the people, such modern Muslim theocracies. There the rulers welcome belief in God since they are the ones who dictate what God says, so the state still retains ultimate power. This is why Hitler made a deal with the Catholic Church -- religion was acceptable as long as it was under his control. Otherwise, the state is supreme.
But because these modern totalitarian regimes put themselves in place of God in the eyes of the people, atheism is somehow to blame. Although there was no longer a supernatural element, they are effectively religious, as their god is the state. The Juche ideology of North Korea is a quasi-religion (a.k.a., political religion). Kim Il-sung is revered as the deity, and Kim Jong-il is the living prophet.
I wasn’t giving an opinion, I was stating a fact.
Atheists vote liberal and religious people vote conservative, that is the primary voter division between the Democrats and Republicans.