The first problem is that you equate voting for McCain with actually being conservative. The second problem is that you equate voting for Obama with actually being liberal.
I have given you a clear reason why many atheists did not vote for McCain despite having more conservative views. I couldn't stand big-government McCain, soft on illegal immigration. Unfortunately, I felt I had to place a strategic vote against Obama since I was in a state that could go either way. Other non-liberal atheists also didn't want to throw away their vote, but couldn't vote Republican for the religious reason.
If nothing else, take this lesson from this thread: Do not purposely alienate potential allies. It can cost you elections.
Welcome to our country, where conservatives vote Republican and liberals vote Democrat.