Double standard on religion and politics?

Have you ever wondered why it seems that Democratic candidates are so often pictured giving speeches/sermons in churches with hardly a word of criticism, but when a church takes a conservative moral stand that also happens to be critical of a candidate's position on the issues there is an uproar? John Hinderaker at Powerline has an interesting take on this, complete with pictures, that include "Kerry/Edwards" signs being waved in a church service this weekend.