CathInfo.com

... sɛҳuąƖ "rigorism" is opposed by many traditional  Catholics online more strongly and more viscerally than most other unpopular opinions.

Hardly.

Do you even know the stuff Heitanen was spewing?

Heitanen taught that married people kissing each other was a sin.
He taught that doing anything to "stoke desire", even things like having sufficient lighting to see one's spouse naked to any degree, was sinful.
I think he even required that you pray and make acts of the will to reject any pleasure during coitus itself!

Complete garbage, from a Catholic perspective.
I'm sorry, but such teachings make a mockery of the Catholic Church's conservative (and unpopular nowadays) teachings on sex.

His website -- which obsessed on issues of sex and little else -- was more consonant with Puritanism and Manichaeism (Good God made the soul, evil "god" made the body and the material world) than Catholicism.

I'll give you another hint, Matto --

Often times an individual will form too strict a position on something, due to sins in his own past. The person carries baggage, and is trying to make up for what he did in the past with extra strictness today.

For example, many sedevacantists and Dimond Bros. followers exaggerate the evils and status of the Novus Ordo Mass because they once attended it, and are still smarting from the betrayal of their priests and angry at what was taken from them. Also consider that many converts to Tradition still bear many scars from their days in the Novus Ordo, including divorces, annulments, being involuntarily single, and/or being in a bad marriage. They chose from the Novus Ordo for their spouse, and therefore they chose poorly. And now they are angry. They are also angry at being "behind" in knowledge and virtue compared to other Trads their age.

And of course there's the classic example of the man who has a sɛҳuąƖ "past" and now strives to make sure he's on the right side by being extra strict. He reasons that if he goes too far, so much the better, to A) show God his sincerity and good will and B) do penance for his past sins

Such is human, but still results in rigorism and even error. This is especially bad when it causes individuals to judge and condemn their fellow Catholics, who are more objective and balanced.

But Lad, you yourself are condemned as a rigorist and a heretic for rejecting NFP even though you do not go as far as Jerome.

My opinion on NFP is based on reason ... applying the teaching of Pope Pius IX in Casti Conubii.  I apply syllogisms to his teaching.  This has nothing to do with rigorism, which is an emotional attachment to the more strict opinion on everything.  It's related to scruples.

What the heck are you talking about, claiming that I am a "heretic" for rejecting NFP.  Permissibility of NFP has never been dogmatically declared; all we have is the opining of Pius XII before a group of midwives.

You admitted that you were not altogether observant of the 6th and 9th commandments in your earlier days, so I submit that your rigorism -- as is often the case -- represents an emotional pendulum shift for you against your prior lifestyle.  Try to take the emotion out of it.