Chance is not a principle, much less a guiding principle. Taken in broad strokes, chance, or a chaotic universe, is a dynamic system, which will respond to the laws it inherents from it's inception. Moral judgements arise from human concerns, as best I am able to detect. Your argument make the a priori assumption that morality arises from some source outside human concerns--you assume the victory of your argument to make your argument.
If this is true, then why insist that the definition of science entails predicting results that we can fit into a theory? How are you going to separate "chance" from "predicatability" and still be a scientist?