The dark shadow we seem to see in the distance is not really a mountain ahead but the shadow of the mountain behind - a shadow from the past thrown forward into our future. It is a dark sludge of historical sectarianism. We can leave it behind us if we wish.
I hope we will not so characterize religious people as being so narrow and so biased towards people not of their own religion that they cannot even work with them in this common cause to which you say they are committed.