I’m not sure that they meant that all the secular are atheists, but of course all atheists would be in that grouping.
It is clear that atheists, or secular are overwhelmingly liberal, unlike the committed Christians that are overwhelmingly conservative.
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.