If your prior belief points strongly in one direction, it is completely rational to require strong weight of evidence in order to update it to point to the other direction.

And yes, it's a completely reasonable prior belief for a person who is not already versed in medical imaging literature.

I often find that people who study this literature have bad attitudes like yours. You should be grateful that there are people out there who value intellectual honesty enough to acknowledge when a result is a result and to change their beliefs. Instead I get two different people showing up to insult me.