“Value judgements are hard to argue with--is green a better colour than blue? Should we have justice or peace? Thus, we all seek to make our value preferences into facts, rather than opinions.” Link
What your are doing here is exactly was Pope Benedict was addressing in his controversial Address at the University of Regensburg. He said,
The subject then decides, on the basis of his experiences, what he considers tenable in matters of religion, and the subjective "conscience" becomes the sole arbiter of what is ethical. In this way, though, ethics and religion lose their power to create a community and become a completely personal matter. This is a dangerous state of affairs for humanity, as we see from the disturbing pathologies of religion and reason which necessarily erupt when reason is so reduced that questions of religion and ethics no longer concern it. Attempts to construct an ethic from the rules of evolution or from psychology and sociology, end up being simply inadequate.Not all values are subjective preferences. Some values are universally held and to deny them is to deny the best of what it is to be human. Take the value of courage, can you imagine a society were cowardice was held with more value than courage? The answer is not to try less, but like pope Benedict explained we need to broaden the use of reason to bring the important questions that religion and ethics ask out of the subjective realm.