John 8-9

"You were steeped in sin at birth; how dare you lecture us!"

yelled the Pharisees at the formerly blind man.

This exclamation shows pride, for their own life accomplishments, for their assertions of Jesus' identity, for their position.

But "all have sinned and fall short of the glory of God." Rom 3:23. All have gone and put their own selfish ways above the ways of God, our plans above His, our goals and desires above His.

Now, if this was the only verse you could argue that they wouldn't have heard this before, but it is not just in the New Testament. Verses describing how sinful nature has been passed on throughout the generations since the very first disobedience and how none are good are found throughout the Old Testament.

Ecc 7:20 - "Not a single person on earth is always good and never sins."
Prov 20:9 - "Who can say, "I have kept my heart pure; I am clean and without sin"?"
Psa 51:5 - "Surely I was sinful at birth, sinful from the time my mother conceived me."
Job 15:14 - "What are mortals, that they could be pure, or those born of woman, that they could be righteous?"

And sin was so rampant that at one point God flooded the earth.

Sin. The ultimate end of those who have sin, is separation from God who is without. Can a mortal be more righteous than God? Can even a strong man be more pure than his Maker? (Job 4:17)

But God was patient with us, and also spoke through the prophets of the way out of this sin problem. Although sin was as a stain that could not be removed, it would be bleached.

"Come now, and let us reason together, saith the LORD: though your sins be as scarlet, they shall be as white as snow; though they be red like crimson, they shall be as wool." Isa 1:18

But not by us.

"Who can bring what is pure from the impure? No one!" Job 14:4

Only He who is pure can purify. Only a clean sponge with soap can clean dirty dishes. And even then it is only by the sponge taking on the dirt of the dishes.

Isa 53:4-5

"Surely he took up our pain
    and bore our suffering,
yet we considered him punished by God,
    stricken by him, and afflicted^.
But he was pierced for our transgressions,
    he was crushed for our iniquities;
the punishment that brought us peace was on him,
    and by his wounds we are healed."

All that to say the way they spoke to the formerly blind man is arrogant and incorrect. We all need to have our eyes opened and receive forgiveness for sins.