The problem with people knowing about a politic's religious beliefs is that some groups are told to vote for people only because of their faith.
For example, I remember my great-aunt telling everybody not to vote for somebody because they would start the end of the world. That is just ridiculous.
I thought of a rule for voting. Anyone with an IQ of under 120 cannot vote. That would definitely solve any ignorant voting. But as you were saying, I sure want to know if the person I am voting for is a crazy religious freak.