Just bullshit

It is the foul doctrine of "original sin".
The idea being that the sin of Eve in eating of the forbidden fruit is passed down through the generations to all of her decedents.
Of course when believing in Adam and Eve went out of fashion, original sin came to mean that the idea that sex is inherently sinful, therefore anyone conceived by sex inherits the sexual sin of their parents lust.

So, depending on your denomination, everyone is born carrying at least two Hell worthy sins from which they need the salvation of Christ to escape hell fire and damnation.

Christianity depends on people being labled as sinners.

If they don't have the 'disease' then how can they be sold the cure? Christianity only WORKS if you can convince everyone they will go to hell without the church to 'forgive' them.

It is the logic of the Nazis.
If you wish to use, exploit, and abuse people. Then you must first find a way to convince everybody that some people are less than perfect and subhuman, and therefore deserving of abuse, and not of defense. The Nazis directed that idea at Jews, Romany, Blacks and the disabled etc. But they were late comers to the show, and missed the trick played by the Churches, who managed to direct that logic at the whole human race.

Remember the motto above the gate where slaves went in was. "Work makes you free." And slaving for the churches, makes you free from guilt and the threats of hell.

You have to be a sinner so Jesus can save you from going to hell for your sins. If you are not a sinner, why do you need Jesus? So, you need to be a sinner so you will need Jesus and be required to give 10% of your income to the church to demonstrate that you believe in Jesus enough to save you from hell. Now, that makes sense, right?

According to their folklore, Jesus was a Christian and he was not a sinner.

"sin" is bullshit. there's no such thing. no "action that is universally declared as bad". each culture has its' own definition of bad behavior so the rules are MAN-made, not natural.