The Jews did not believe that he had been blind and had received his sight until they called the parents of the man who had received his sight and asked them. Is this your son who you say was born blind? How then does he now see? His parents answered We know that this is our son and that he was born blind. But how he now sees we do not know nor do we know who opened his eyes. Ask him he is of age. He will speak for himself. His parents said these things because they feared the Jews for the Jews had already agreed that if anyone should confess Jesus to be Christ he was to be put out of the synagogue. Therefore his parents said He is of age ask him. So for the second time they called the man who had been blind and said to him Give glory to God. We know that this man is a sinner. He answered Whether he is a sinner I do not know. One thing I do know that though I was blind now I see John 9.

The Jews even though the proof dont believe and are being blind by their bias against Jesus and their belief that he was a sinner. The Jews created the fear to be kicked out of the synagogue to protect their religion and keep people against Jesus.