Among those who criticise Christianity one of the biggest complaints is its exclusivity. How dare you say that you are right and everybody else is wrong? Sometimes the concept is phrased in a different way: All major religions are equally valid and basically teach the same thing.
But when we ask those who think that all religions lead to God, how they would define this God, they usually reply that he is an all-loving spirit in the universe or some such inoffensive definition. They will insist that individual doctrines do not matter. However, such a view of God is at odds with the five major faiths. Buddhism does not believe in a personal God at all, Hinduism believes in many gods while the three monotheistic religions, Judaism, Christianity and Islam all believe in a God that holds people to account for their beliefs and practices - though each has a different view on which beliefs and practices are essential. All the sceptics are doing is trying to create a sixth religion, the major doctrine of which is that doctrine does not matter (except for this doctrine, of course).
Sometimes the illustration is used of the blind men and the elephant. Each describes God according to the part of the animal he can feel - the leg, the drunk, the flank, the tail - but none can 'see' the whole animal. What is wrong with this illustration is that it assumes that the critic can see the whole elephant. In other words the critic arrogantly assumes for himself a position of superiority.
Others will say that what we believe is culturally conditioned. I might be a Christian because I was born in England, but were I to have been born in Morocco I would have been a Muslim. Everything is relative, they say. This statement proves too much, for it means that even the sceptic is subject to such relativism. He only believes it to be true because of the way he has been brought up.
Post-modernists tell us that it is arrogant to insist our religion is right and to try and convert others to it. They say that all religious claims to have a better view of things are arrogant and wrong. Once again this proves too much, for on this basis, this very same claim is arrogant and wrong.
Is any religious claim to be better than any other bound to be untrue because of such reasons? Such a belief would be a religious belief and itself be bound to be untrue.
Sceptics (or Skeptics) seem very keen that Christians should not proselytize. Why should they care? Only because they are proselytizers themselves of what is in fact another religion (even if they don't recognize it as such).