Democracy demands that the religiously motivated translate their concerns in to universal, rather than religion-specific, values... it requires that their proposals be subject to argument and amenable to reason.
Now I may be opposed to abortion for religious reasons, to take one example, but if I seek to pass a law banning the practice, I cannot simply point to the teachings of my church or evoke God's will. I have to explain why abortion violates some principle that is accessible to people of all faiths, including those with no faith at all.
