I want to thank Sandefur especially for the link to this very interesting site by Larry Arnhart. This post in particular raises some very important points.
Proving moral truths can be a very complicated matter; so it would be wise to be very skeptical of anyone who claims to have "easy answers" in this regard. One claim that is often bandied about is that the Bible -- meaning taken as a literal, inerrant whole -- contains those answers. Not so. On some of the most elementary issues of morality, the Bible, read in this respect, falters. As Arnhart writes:
Holloway repeatedly asserts that religion supports some very specific moral positions--such as condemning slavery. But he never cites any specific religious texts to show how they necessarily support the moral positions that he favors. The case of slavery and "universalism" illustrates the problem. He assumes that religion necessitates a "universal" morality that would deny the morality of slavery. But many religious traditions have allowed slavery, and the Bible never condemns slavery or calls for its abolition. On the contrary, in the American debate over slavery, Christian defenders of slavery were able to cite specific biblical passages in both the Old Testament and the New Testament supporting slavery. Opponents of slavery had to argue that general doctrines such as the creation of human beings in God's image implicitly denied the justice of slavery. But they could never cite any specific passage of the Bible for their position. Here's a clear case of where the moral teaching of the Bible depends on our coming to it with a prior moral understanding that we then read into the Bible.
Moreover, the "universalism" of the Bible is in doubt. I don't see a universal morality in the Old Testament. Moses ordering the slaughter of the innocent Mideanite women and children, for example, manifests a xenophobia that runs through much of the Old Testament.
Now, of course, the New Testament does seem more inclined to a universal humanitarianism. But the Book of Revelation teaches that at the end of history the saints will destroy the Antichrist and the unbelievers in bloody battle. The bloodiness of this vision has been dramatized throughout the history of Christianity. (See, for example, Tim LaHaye's popular LEFT BEHIND novels.)
Holloway speaks of the moral universalism required for opposing Nazism. Is there any evidence that those who rescued Jews in World War II were all moved by religious belief? My impression is that religious belief was not decisive for the rescuers. And, of course, there is a continuing controversy over whether the Christian churches in Europe did enough to oppose Hitler. The German Lutheran Church was inclined to interpret the 13th Chapter of Romans as dictating obedience to the authorities. Martin Luther himself was brutal in his expression of anti-Semitism. How would Holloway explain cases like this? Would he say that the true doctrines of biblical religion always require universal love, and therefore any behavior by a biblical believer that violates universal love is based on a misinterpretation of biblical doctrine?