http://introiboadaltaredei2.blogspot.com/2019/10/multiplication-problems.html

What are your thoughts?  He essentially claims that the church has taught NFP infallibly through the magisterium.  

I hope to start a civil discussion

There are some who say it is at least a venial sin even if it is used for a grave cause. This position is explained on the following blog post: http://philotheaonphire.blogspot.com/

However, I know there are some good priests like Father Chazal who are argue that it can licitly be used if there is grave cause (ie. real danger of death). In any case, almost
all traditional Catholic priests would agree that complete abstinence is generally more virtuous than using NFP.  

It is a matter of fact-- not opinion-- that the Holy Offices of Pope Pius IX (1853), Pope Leo XIII (1880), Pope Pius XI (1932), and of course Pope Pius XII, all taught that periodic continence can be lawful.  It is also a matter of fact-- not opinion-- that during that hundred year period (1853-Pius XII), theologians unanimously agreed on its intrinsic lawfulness (although they did disagree on some of the upstream principles and downstream applications).  It is also a matter of fact-- not opinion-- that theologians were never rebuked for believing it to be a lawful practice.
.
Given the facts, I would agree that the Church infallibly teaches that periodic continence can be lawful to use.  The alternative is to suppose that a hundred years worth of popes and theologians universally erred on the matter.  Let's keep in mind who those popes are-- not just Pius XII (as it is so often ignorantly alleged), but Pope Pius IX and Pope Leo XIII.  Pope St. Pius X, a militant pope on moral and doctrinal matters, did not censure or rebuke theologians for teaching it.  Pope Pius XI is included among these popes as well (which should give anyone who thinks that Casti Connubii denies the lawfulness of periodic continence pause, since no sooner was the ink dry on that encyclical than did the same pope explicitly confirm its lawfulness via the Holy Office).  The scope of periodic continence being taught exceeds the scope of religious liberty being taught both in time and space. 
.
Of course, it is one thing to simply reserve judgment on whether or not this amounts to infallible teaching; it is another thing altogether to accuse such orthodox men, over such a long period of time, as having taught grave or even heretical moral theology. 
.
Importantly, I should point out that an expression like "the Church teaches periodic continence" should be understood to simply mean that the Church teaches it can be lawful to use.  The Novus Ordo seems by all accounts to teach something very different, they seem to teach that it ought to be used in some general away.  The Catholic Church has never taught that, she has merely taught that there is nothing intrinsically evil about it, and regularly warned that it is something that should be taken seriously, not taught (as a method) publicly or indiscriminately, and only used when there is a commensurate reason.
.

Yes.  NFP is not intrinsically evil as is straight out contraception.

That's not correct.  What is not intrinsically evil is abstaining from marital relations.  But the formal motive is what makes it evil ... and what turns mere abstinence into NFP.  Evil is evil, and sin is sin.  If someone abstains only during a certain time in order to avoid conception, the formal intent there is to subordinate the primary ends of marriage to the secondary ... which Pope Pius XI denounced as sinful in his encyclical Casti Conubii.

That's not correct.  What is not intrinsically evil is abstaining from marital relations.  But the formal motive is what makes it evil ... and what turns mere abstinence into NFP.  Evil is evil, and sin is sin.  If someone abstains only during a certain time in order to avoid conception, the formal intent there is to subordinate the primary ends of marriage to the secondary ... which Pope Pius XI denounced as sinful in his encyclical Casti Conubii.

Lad, it is fitting that you should bring up that argument now, since we are nearly at the one year anniversary of me having argued against you that Casti Connubii contains no such denouncement.  Has a year been long enough for you to develop a response to my criticism? :)

Lad, it is fitting that you should bring up that argument now, since we are nearly at the one year anniversary of me having argued against you that Casti Connubii contains no such denouncement.  Has a year been long enough for you to develop a response to my criticism? :)

What CC teaches is right there in black and white.  It is sinful to subordinate the primary end to the secondary.  If attempting to eliminate the primary while enjoying the secondary is not subordination, than nothing is.

You falsely claimed that SUBordination is not in the original text, except that it is.  "due/necessary ordering toward the primary end".  That is what phrase means that, being the secondary end, it must be ordered to the primary end ... correctly and appropriately translated in approved translations as subordinated.  That was the big criticism of Vatican II from the conservative Fathers group, that V2 tried to make the primary and secondary ends of marriage to be co-primary ends, whereas Traditional Catholic theology has always taught that the secondary were SUBordinate to the primary.  And I explained the context of your completely out-of-context use of the Holy Office ruling.  That had nothing to do with any principled acceptance of NFP whatsoever.  In fact, the language backs up the Church's disapproval of NFP.

I already responded to you, including one long multiple-paragraph post and several smaller posts addressing each one of your false points.  I clearly addressed how your wore purposely conflating the two separate principles outlined by Pius XI, claiming that a mere physical completion of the act in the natural way was in fact identical to having the proper motive regarding the ends of the act ... which is utterly absurd and preposterous.  You make now allowance whatsoever for the distinction between the material act and the formal motive behind it, which would be rejected by all Catholic theologians.  This merely shows your desperation in attempting to justify this sinful activity.  Please be advised that by promoting this sinful activity, you yourself will be judged by God.

What CC teaches is right there in black and white.  It is sinful to subordinate the primary end to the secondary.  If attempting to eliminate the primary while enjoying the secondary is not subordination, than nothing is.

.
Here, let me refresh your memory: https://www.cathinfo.com/general-discussion/questions-on-sex-and-specifically-the-role-of-procreation/msg630779/#msg630779
.
My position is that the subordination of ends and preservation of the nature of the act are not separable, but that if the act is preserved (i.e., performed without contraceptive intervention) the ends are ipso facto subordinated.  I base this reading on the text itself: in Latin and in the Denzinger/DeFerrari translation to English, and the commentary on the encyclical provided by its drafter, Fr. Vermeersch, who supports the way that I understand it rather than the way that you understand it.
.
Your position-- that there is a distinction between the preservation of the act and the ordering of ends-- depends entirely on the integrity of the Pieran Press translation of Casti Connubii from the 1990s, which integrity I have directly challenged, and which challenge you have never responded to (except by merely re-asserting the apparent "obviousness" of the matter).