I would agree with the notion that a candidate's religious views are only important insofar as they will or do influence his/her political decisions and as they may become somehow ratified or legislated during his or her time in office.
We can reasonably discuss his/her religious views as they inform his/her moral views because we can expect certain decisions to be made based on those preconceived, systematically defined moral systems.
It's worth pointing out that everyone has a moral context, a moral basis on which decisions are based. For some this context is religious in orientation and for others it is not religious at all.
The question we have to ask of our leaders should be more driven by what they will do than why they will do it, as pointed out in the post above.
If a candidate's religious views inform us about what he/she will do in office then discussing and weighing those views is appropriate.