My thought is the parents reacted as they did for fear of the roman government. What say you?
This is John, Chap 9 as I recall. And their fear had nothing to do with the Roman Gov't, but Pharisseical courts. It had to do w/ fear of being ejected from the synogogue if they acknowledged that their son was indeed cured by Jesus.
Instead of reacting like 'normal' parents, joyful for a sighted son, the reacted like parents today really do react all the time: the care about what others think more than they care about what is right. This is why so many parents cheat regarding school projects their kids should be doing alone, for example.
So, when they were being interrogated, they told the religious authorities that yes indeed, He was their son ... but that he was old enough to speak for himself about 'who' cured him. But rationally, does this make sense if you know your cured was blind from birth? Only if you know the power of the fear of being on the outside looking in.
It was this echo of 'normal' 2000 years ago, that is so in tune w/ 'normal' today, as parents tear at each other, and continue to abort kids, and continue to watch TV, and struggle to get that cul de sac palace ....
It was reading this echo of 'normal' that massively increased the credibility of the New Testament for me.
They were more afraid of the Pharisees & Priests. Rome probably didn't give a hoot unless said Healer was going to declare Himself Caesar.