Correlation is not the same as causation.
Being a liberal doesn't make you believe in evolution. And the opposite is not true either. But the fact remains, conservatives are more likely to disbelieve in evolution. This isn't the first poll that shows that, and the belief is also widely apparent from personal experiences and anecdotal sources.
There is a statistical connection that is very real, and there are very real reasons for it. But you are right in one sense, political and religious beliefs are disconnected. It is possible to be an evolution-believing Republican or a Creationist Democrat. But it is unlikely, and becoming more so.
BTW, you responded to my post while I was doing some last-minute edits. You might want to re-read it.