When you don't understand the science yourself and can't properly weigh the risks / benefits it seems fairly reasonable to rely on experts.

In this case, the parents likely did not have the information necessary to make a decision about their own offspring (especially since they were lied to).

As far as legal/societal decision making, I don't think we have a better solution than relying on experts. What is the alternative? Unless you are only talking about using personal morals for the purpose of discussing right/wrong rather than actually making decisions based on them.

Well, they seem to have done so, as have many believers of scientism. As well as the doctors who forcible sterilized and lobotomized undesirables. WE certainly cannot though. Humanity needs some of us to keep true north.