All their lives they had believed that his blindness was their fault, was due to some sin on their part. So, to be told one thing all your life, to have all that guilt and then to suddenly be told for the first time, Sorry. None of the above is correct. It was not due to your sin or that of your parents. And with those very words the healing began in his life and that of his parents.
Guilt is an awful thing to live with.
It is a heavy burden that can crush us. Sometimes it is our responsibility, what we have done to deserve it. It can and should then led us to bended knee before God. This is good guilt. It leads to repentance and change of life.