The Christian philosopher has a perfect right to the point of view and prephilosophical assumptions he brings to philosophic work; the fact that these are not widely shared outside the Christian or theistic community is interesting but fundamentally irrelevant.
Alvin PlantingaTo show that there are natural processes that produce religious belief does nothing, so far, to discredit it; perhaps God designed us in such a way that it is by virtue of those processes that we come to have knowledge of him.
Alvin PlantingaSuppose we concede that if I had been born of Muslim parents in Morocco rather than Christian parents in Michigan, my beliefs would be quite different. [But] the same goes for the pluralist...If the pluralist had been born in [Morocco] he probably wouldn't be a pluralist. Does it follow that...his pluralist beliefs are produced in him by an unreliable belief-producing process?
Alvin Plantinga