Religion does not supply an a priori unchanging objective a system of morality.

The argument you present here is a complete straw man. Most if not all of the things you cite are not part of the unchanging moral code that Catholics believe in dogmatically, and Protestants have no reason to claim that anything not written in the Bible isn't subject to change, so this is basically a question of Catholic moral theology within a Christian context. I'll throw out there that for Jews and Muslims the law is the law and that's it, but this seems overly rigid and lacks the response to change necessary for long term stability and growth as a religious body. For Protestants morality can and frequently does change, and any Protestant making a claim about specific unchanging a priori ethics, especially for anything extrabiblical, are in serious need of a theology course. I'm going to address your parade of straw men one at a time before I present a more cogent look at what an unchanging ethical system really is. The status of unbaptised infants isn't an ethical question, but even if it were no dogmatic teaching was ever formulated on this issue for or against it. Your torture point in the Protestant column is specious, because you seem to be taking George W. Bush as a paragon of Protestant ethical thought which is horrifying to every Protestant outside of fundamentalist Evangelical Christianity. The use of torture was actually though humane by most people in the Middle Ages in comparison to the mob killings which were far more common. Even when torturing people it was not used to extract confessions which could be used in court (the tortured had been found guilty already), and there were specific laws limiting its use. Like the Death Penalty, the Church has reconsidered what is humane treatment over time as the philosophy of personhood and rights has developed, but it has always taught that there's some basic level of legal protection all people should enjoy. Genocide is the systematic intentional killing of a group of people. This was unknown in Catholic circles, or in fact almost any circles, until the modern era. Slavery is another issue that did not seem wrong to Catholics in 325 because they had no notion of rights or freedom. It is not until much later that the notion Slavery is wrong developed. Usery is unethical collecting of interest on debts. Loan sharking, predatory lending, exploiting the poor, and any other immoral charging of rates has always been held to be immoral. Before modern financial systems, all usery was predatory and exploitive, because there was no notion that lending money for profit was actually beneficial to society. Remember that modern economics is only as old as the United States. We were never for socialism as a political system. Nobody ever was. No idea where you got this from. Again, George Bush and the political right that calls itself Christian are not examples of moral theologians. Most theologians only oppose the drug trade on the grounds that it is illegal. How to use which drugs is fundamentally a private moral choice that isn't universally applied. "For public schools" isn't a moral choice and nobody opposed them on political grounds. The Catholics only had problems with them in the US, and then because it was the policy of American schools to teach Protestant Religious Education with the King James Bible in public schools, so Catholics were specifically discriminated against and used Catholic lower schools to break out of the system. "For freedom of religion" is again not a moral concern. It's a practical statement about how society should be run. And any society has certain beliefs that it finds unacceptable and punishes or socially stigmatizes. In the US, denying the holocaust or advancing the position that black people are inferior to white people is as much a heresy as Catharism was in the 1300s. A true a priori moral system is not a series of unchanging positive or negative injunctions, it's a basic set of principles that moral reasoning can be based on. The Ten Commandments, the Beatitudes, the Works of Mercy, the Capitol Sins and Virtues, the Greatest Commandments, these are the unchanging things that create a moral framework. Loving you neighbour in 1007 looked a lot different than it does in 2007, and I imagine in 3007 it will look profoundly different again, but the key to moral reasoning isn't any specific action or non-action, it's the constant guideline that we should love our neighbour as we love ourselves. You've confused individual moral issues which change and develop, along with people's perceptions, with a concrete set of moral ideals which do not and have not changed, and which allow moral reasoning in any situation which takes into account developments in other areas of human understanding. Just as American laws have changed drastically but the Constitution remains basically the same, individual moral questions have had different answers, but the bases for these answers have not wavered.