Those who framed our Constitution lived during an age when religious intolerance dominated world events, causing war after war after war and the deaths of multitudes. They understood on a personal level what can happen when the politically ambitious convince people that god is on their side and use religion to justify persecution and genocide. That's why they made the separation of church and state a keystone in our Constitution.
The line between religious belief (or the lack thereof) and governmental policy needs to be clear and firmly defended.
I find recent trends towards blurring that line increasingly alarming. It is especially troubling that the same people who champion strict Constitutionalism in some situations are willing to ignore its most key component when it suits their agenda.