The true message of Demon Haunted World. If it is science we can all work on the problems and make the world a better place. If it is demons all you can do is obey someone who tells you which side is good and which is evil.
Even as a non believer I can see that the parable of the golden calf will be true here. By hitching the church to a political party they take on risk. When people feel wronged by the party they will feel wronged by their church. If they feel wronged enough to leave, that damages the church. So, because they worshipped a false idol they get hurt.