Mercator.net has published an article by a Lutheran scholar, Dr Allan Carlson PhD, the founder and president of the Howard Center for Family, Religion, and Society (See: Be fruitful and multiply and have 1.7 kids ... and a dog? The article was previously published in the journal Family Policy in June 1999.)
The essay raises some fascinating questions regarding Humanae Vitae. As Dr Carlson rightly points out, one of Luther's complaints about the Catholic Church was its teaching that vowed chastity or celibacy was in principle a superior state to marriage. In response, the 24th session of the Council of Trent, in 1563, duly defined in the canons on the sacrament of matrimony (canon 10) that
If any one says, that the marriage state is to be placed above the state of virginity, or of celibacy, and that it is not better and more blessed to remain in virginity, or in celibacy, than to be united in matrimony; let him be anathema.(Remember that this is de fide teaching which we are bound to believe with the assent of faith. If we find it surprising today, it is our job to ponder how to reconcile our thinking with the teaching of the Church, not to adjust the teaching of the Church to our thinking.)
What is especially relevant today is that Luther's reason for opposing celibacy was not simply his outrage at clerical concubinage and the scandal given, but more fundamentally his enthusiastic support for marriage and the family, and particularly for the procreation of children.
Although as Catholics we would hold that Luther's opposition to celibacy and virginity was misguided, it is interesting to note that he agreed entirely with the doctrine that the primary end of marriage is procreation - something denied by the acceptance of contraception in many protestant communities (who would take their stand on the reformation of Luther and Calvin) and indeed by many Catholics who might think it "an ecumenical matter" to deny Humanae Vitae.
In case there is any doubt, consider this quotation from Luther which is included in the article:
How great, therefore, the wickedness of [fallen] human nature is! How many girls there are who prevent conception and kill and expel tender fetuses, although procreation is the work of God! Indeed, some spouses who marry and live together… have various ends in mind, but rarely children.(I would be interested to have a source for that quotation - not because I would in any way doubt its authenticity, but because it would be useful to quote it in the future.)
When speaking in friendship to our evangelical protestant brothers and sisters, it would be worthwhile asking why they do not affirm Luther's position on contraception which was essentially the same as that taught in Casti Connubii and Humanae Vitae.