Notes

Fitrah the inherit nature of the human being. It's believed in Islam that the inherit nature of every human being is good and it's diseased societies that Effect the nature in a diseased way. Different from the Christian belief of a corrupt nature. Islam there is a black seed in the heart, a pull towards desire, but the overall nature is good.
In the 1970's there were many places here in America where people couldn't live together unless they were married, anything other than that was not acceptable. How much has changed since then.
There are a lot of variables that explain why people do what they do, it's not just 1 factor, it's not black and white but nurturing the fitrah, the upbringing plays a major role in it, there's no doubt about that.
First thing you find in books of jurisprudence is purity , and there are 2 aspects to that, spiritual and ritual purity, Meccan stage before medinah stage, so before any legal rulings are applied there is a process of purification and nourishment of the soul that takes place. Then the rules start to make sense, you can't apply criminal punishment before all of those other stages happen.

Fitrat Allah al lathe fatar... Leaning towards all that Allah ordained from good, Unless the fitrah is changing. Regardless. Of whether the misguidance is in belief or actions. So for example you wouldn't find a young child that knows how to lie until they learn this behavior from others.
So Allah created mankind with the inherent nature to believe in him, So everything you find in the quran reaffirms the fitrah and protects it from corruption.
So the belief that's in the fitrah is then reaffirmed by the revelation, certain aspects only known through revelation. The fitrah says higher power, creator, God - so some say God is spirit, or a force, nature, or something other than that, the revelation comes and clarify who the creator is, so the belief that's in the fitrah is clarified and explained in the revelation.
The fitrah has to be protected just as the quran and sunnah is protected from change, it's a combination of both that leads to success.
Firah - sibghah always singular indicating 1 fitrah, similarly animals have fitrah doesn't change because didn't will shaytan for them, desires, etc.
hayaa for example is there by origin and slowly lost when sins are committed...
La tabdeel le khalq illah- warning from changing the qualities and nature that Allah created us with, When the fitrah is changed it can no longer accept the truth. Just like if a cup is bent, cracked and broken it can't hold water.
Wa la udillanahum- Fala ybuaddilunna khalq Allah - changing their nature sO thT they will love to lie, to be corrupt, lean towards evil, shaytan took upon himself changing the fitrah.