Those lukewarm "Catholics" who haven't even considered that NFP might be sinful and researched the issue will be repaid for all the pleasures they partook in this life unlawfully.
https://schismatic-home-aloner.com/natural-family-planning-nfp/
Not gonna lie... having reference to the Dimond Brothers does NOT help your case any.
Aside from Creation and a few other basics ("a broken clock is right twice a day", plus we Catholics agree with Mormons, Baptists, and many other heretics on countless elements of the Natural Law), they get just about everything else wrong. They are the modern-day Pharisees, with all the same faults Our Lord condemned the Pharisees for: Making up laws, condemning others unjustly, rash judgment, cutting themselves off from God, forgetting Charity, etc.
If you want to make your point, I would avoid bringing the Dimond Brothers into it. Unless you want to have the opposite effect :)
I'm not kidding. The Dimond Brothers are SO bad, that if a Catholic immediately dismissed your criticism of NFP as "Oh, that's more Dimond Brothers extremist nonsense" THEY WOULD BE JUSTIFIED BEFORE GOD IN DOING SO. Even if that was their only reason.
If I dismissed something being pushed by (((Red Sea Pedestrians))) and God wouldn't hold it against me for failing to look into it, the same would apply to other villains like the Dimond Brothers.
After all, when a mouthpiece has been proven vile and wrong 100 times, you can be at least MORALLY certain (maybe not metaphysically or scientifically certain) that they are wrong the 101st time. It's about moral certainty -- enough to base one's actions on.
P.S.
"will be repaid for all the pleasures they partook in this life unlawfully"Is that a quote from the Dimond Brothers, because it sounds like them. If they are your words, then you have ingested too much Dimond poison. "Lie down with dogs, rise up with fleas." Because those words, just reading them in isolation, sound like a person a bit too
personally invested, filled with bitterness, anger, and hatred. If one's motivation is God/truth/goodness, why not just make your case without such threats? The sentence I quoted seems to be dripping with bitterness and maybe even jealousy.
What do you think, Dear Reader? Am I off base on this?