Pre-Vatican II teaching on NFP, how is it refuted?

Mark, we are familiar with the quotations.  They are not infallible statements; and they are not even Papal statements. They are a few somewhat ambiguous responses from members of the Holy Office before Vatican II and they reflect the growing Modernism that was capturing large parts of the clergy from the time of the late 1800's to Vatican II – as exemplified by the rampant denial of the dogma Outside the Church There is No Salvation found in many theology texts and manuals from the period. So, to reiterate, they are not infallible or binding, and, if they do in fact endorse birth control by means of NFP (as they seem to), they contradict the Magisterial teaching of Pius XI that the primary purpose of marriage and the marriage act is the procreation of children – and that the other purposes or ends of marriage must always be subordinated to the procreation of children. NFP violates this by subordinating the procreation of children to other ends by deliberately trying to avoid it.