I guess an equally good question would be: "adding secularism to politics is it a good thing or a bad thing?"
IMO both can be strongly-held ideologies which are accepted without conclusive proof to support them. And both can affect politics.
Do you think that a politcian should take actions according to their own religious philosophy or belief system?
And do you think politicians should wear their religious beliefs on their sleeve for everyone to see and vote for?
I think a politician should take actions according to his political beliefs and those of the people who have elected him to represent them. If this person's religion, ethnicity, sexuality, etc. influence his politics than so be it. So long as the people know what they're voting for.
I guess it depends how much the religion influences his political beliefs and how he will vote. If an MP will vote against embryonic stem cell research because of his religious beliefs, people have a right to know. But beyond that, i.e. privately-held religious beliefs that do not affect his politics, I don't think it's important for the public to know or not know- it's irrelevant.
The separation of church and state was argued for by Christians wanting protection from persecution of the state. I think it's ironic that people use "separation of church and state" to try and prevent Christianity from influencing politics, and then advocate measures that would have the State influencing the Church (e.g. the Greens would like to force all churches to hire at least one gay clergy- now I know the issue of sexually active gay clergy is contentious in the church, but suffice it to say that some agree with it and some don't, and those that don't should not be forced to act against their conscience [of course, so long as they're not actually hurting gays], right?)
Really Church and State should not compromise one another. I don't see anything wrong with them influencing each other, but they serve different functions in society and neither should try and control the other. I would not want to live in a theocracy however I wouldn't want to live in an "atheocracy" either (did I just make a new word up? lol)
Oh btw the dark ages- it was Christians who initially fought against that too (the Reformation preceded the Enlightenment).