All he has to do is to sound sure of himself. The worst sort of ignorance isn't when somebody simply doesn't know about something. It's when they don't want to know.
The CRISPR work that is being developed, for instance , has the potential of being a huge healer for genetically-caused birth defects. Maybe if Mr Sanderson had been born with some horrible defect and he wanted to have children, he would change his tune.