There have been at different times and among different people many varying conceptions of the good life. To some extent the differences were amenable to argument; this was when men differed as to the means to achieve a given end. Some think that prison is a good way of preventing crime; others hold that education would be better. A difference of this sort can be decided by sufficient evidence. But some differences cannot be tested in this way. Tolstoy condemned all war; other have held the life of a soldier doing battle for the right to be very noble. Here there was probably involved a real difference as to ends. Those who praised the soldier usually consider the punishment of sinners a good thing in itself; Tolstoy did not think so. On such a matter no argument is possible. I cannot, therefore, prove that my view of the good life is right; I can only state my view and hope that as many as possible will agree. My view is this: The good life is one inspired by love and guided by knowledge.This passage feels right given the lofty ideals in the last sentence, and with the allusion to the doctrine of Hell. It hardly represents relativism as usually understood. If no moral position can be proved, it can hardly be proved from there that we ought not treat one moral postion as superior to another. It would be very tempting to take it up in exhasperation with those who refuse to be argued out of medieval monstrosities. Some such disagreements do seem impossible to solve, and make it tempting to think that there is nothing objective there.
This would be a mistake, though. The problem is that the situation is not a bit different for questions of fact. There are some people who will insist that we ought not think rationally about many questions of fact. I think I have complained enough about William Lane Craig, so instead I will point to Philip Johnson and Ken Ham. Philip Johnson, founder of the Intelligent Design movement, talks about different rationalities and the sham neutrality of rationalism makes me suspect that his Christian fundamentalism isn't open to rational critique. Ken Ham has said as much--while his creationist organization spends it's time trying to provide evidence for creation, he admits that for him, it isn't a matter of evidence. Oh, and don't even get me started on presuppositionalism.
Against these positions, argument is not any more possible than on many moral matters. We may say, with Ethan Allen, that they do not deserve rational argument, but they will respond "I don't care."
In short, though it may be tempting to throw up our hands in the face of moral disagreement, but then we'd have to do the same when facing Philip Johnson and his ilk. Clearly, the existence of Christian fundamentalists does not disprove the existence of objective reality.