"If you were blind, you would not be guilty of sin ..." (John 9:41)

"If you were blind, you would not be guilty of sin; but now that you claim you can see, your guilt remains." (John 9:41)
Jesus is answering the question that arose from Pharisees:
Some Pharisees who were with him heard him say this and asked, "What? Are we blind too?" (John 9:40)
This was said after Jesus stated:
"For judgment I have come into this world, so that the blind will see and those who see will become blind." (John 9:39)

Why are they talking about blindness?

The blindness Jesus is discussing is ignorance. Ignoring reality.

The physical world is a place of consequence. What we do has consequences. When we knowingly hurt someone, that hurt comes back to us in one form or another.

The legal system is a subset of this system. When a person steals or otherwise hurts someone, that person gets punished. But the system does not need the legal system to work: If a child bullies another child and doesn't get turned in, at some point, their bullying will be returned to them. Whether this takes place a year later, two decades later, or a lifetime later, they will face the consequences of hurting someone.

This has also been called "as you sow, so shall you reap." (Gal 6:7 popularized translation) Jesus also stated clearly that this world is a place of consequence, as he spoke to a man whose body he had healed:
“See, you are well again. Stop sinning or something worse may happen to you.” (John 5:14)
The purpose of this consequence system is to teach. The Supreme Being designed the physical world to maintain consequence learning because - as has recently been concluded by education researchers - this is the best method of teaching.

So why do we need this teaching? Just look around at human behavior. Are humans acting kindly towards each other? Yes, a few are. But many humans are mistreating others. Many are harming others, or otherwise taking advantage of others in order to achieve their goals.

What about not being guilty if they were blind?

If a person commits a crime without realizing it, does the court system invoke as severe a punishment upon the person as if they knew they were committing a crime?

They will likely give some punishment, but not nearly as harsh. They would likely give a very light sentence if any at all. Same with parents. Parents would not be as severe in their grounding of a child if the child didn't realize they had done something wrong. They might still scold the child so they would learn, but because there was no awareness, there is little consequence.

This follows God's design. The more information and the higher consciousness a person has, the greater their responsibility to act upon that information. Should a person be given the knowledge that their actions will hurt another and still does it, they will suffer the full consequences. They will be inflicted with a similar fate so they can experience the consequence.

And this, by the way, is the reason that many people are born into suffering. It is not because God is not fair. They are simply experiencing the same suffering they inflicted upon others in a previous lifetime. They are learning what 'how it feels' so to speak.

Why did Jesus call the Pharisees 'hypocrites'?

As Jesus is responding to the Pharisees, he is speaking of the fact that even though they had been given the teachings of the prophets, they were misleading their congregations by not teaching those same truths, and following them within their hearts. He stated this in Matthew:
"Woe to you, teachers of the law and Pharisees, you hypocrites! You build tombs for the prophets and decorate the graves of the righteous." (Matthew 23:29)
The Pharisees were focused upon their salaried political positions, and their interest was in maintaining those positions of authority. This was why they were condemning Jesus. They were not interested in helping others grow spiritually. And since they had been given the knowledge to do so, they would suffer greater responsibility. This is the meaning of Jesus' statement above to these Pharisees.

Jesus, on the other hand, was acting upon and passing on the same teachings of the prophets that came before him. Just as Abraham, David, Solomon, Moses, Joshua, Samuel, Eli, Job, Jonah, Noah, and Ezekiel taught their followers to love and serve the Supreme Being, Jesus was teaching this same instruction.

Jesus was not utilizing this knowledge to gain a position of political authority in the Jewish temple, or seek wealth in the form of a salaried position as did the institutional temple Pharisees and many of today's priests, bishops, popes, cardinals, reverends, preachers, ministers and rabbis do. 

Rather, Jesus saw himself as a humble servant of God and sought only to please the Supreme Being by passing on the instructions of those representatives of God before him.

Consider, for example, Moses' instruction:
"Love the LORD your God with all your heart and with all your soul and with all your strength." (Deut. 6:5)
Now consider Jesus' instruction:
"'Love the Lord your God with all your heart and with all your soul and with all your mind.' This is the first and greatest commandment." (Matt. 22:37-38)

*Here is the translation of Jesus' statement according to the Lost Gospels of Jesus:

“If you were blind you would be sinless, but now you say, ‘we see,’ so your sin continues.” (John 9:41)