If truth is true, it binds. But in moral theology, we don't just come up with a list of obligations. Protestant theology is distrustful to the invasion of rational thought with revelation. Barth said that we don't need distinctions in theology. He taught that theology was in the kerygmatic word, in the metaphors, not theological certainties.
Moral theology needs rational conclusions to offer answers to concrete moral issues.
Faith, a humiliation of reason, is not a denial of the intellect. Faith knows the dignity of reason and appeals for an understanding, one which cannot replace faith but support it. Fides quaerens intellectum. The rational reflection on the presence of God in human activity doesn't give us proofs for moral activity. We cannot prove in a scientifically modern way the truth of the Mystical Body.