Religion in "Big Society"

With the Pope’s arrival for a four day state visit to the U.K comes a heightened debate about the role of religion in British society.
One of the reasons for Joseph Ratzinger choosing Britain for such a visit is his dismay at the application of equality laws preventing Catholic (or any religion's) discrimination against Homosexuals, which he sees as a secular imposition on the freedom of religion.
The Pope hopes to extend the influence of Catholic Social Teaching in the day to day political and social debate and sees this as a valid contribution to David Cameron’s “Big Society” program which seeks to engage the public and volunteer groups in wider engagement with their communities.
It worries me somewhat that voices within the coalition government, and I suspect Cameron as well, see the greater influence of religious groups in society as an intrinsically good thing. There are several reasons why it isn’t.
In the first instance Religion’s involvement in society rarely comes without strings. Organisations like The Salvation Army work with and feed the homeless, but expect their subjects to listen to Christian messages. Catholic adoption agencies want to exclude same sex couples from their pool of adoptive parents and evangelical groups working with Aids in the third world promote abstinence only policies and deny contraceptives save lives.
While religious groups working for social welfare are well intentioned they cannot help but carry the dogmas of their faith with them and as a result often confound the good they would otherwise do. In many cases they will deny evidence that contradicts their worldview.
This latter point is what makes their usefulness in wider social and ethical debates so moot. The opinions they offer are rooted in scripture and the mores of tribal cultures long past. They are not informed by science unless it happens to confirm their bias and even when they do make concessions to the secular view they want their own exemptions and demand dispensations and respect for their beliefs.
The Pope is already on this visit trying to warn Britain against “aggressive secularism”. During his meeting with the Queen he said…

"Today, the United Kingdom strives to be a modern and multicultural society. In this challenging enterprise, may it always maintain its respect for those traditional values and cultural expressions that more aggressive forms of secularism no longer value or even tolerate."

…by which he means the adoption of societal norms that do not conform to his religious dogma.
There is no reason why religious groups should not have a voice in any debate, but in this they are no different from any special interest group. What we must not do is give them the credibility, degree of deference and public space that enables them to punch above their weight.