The way Mulder’s belief makes the other men in this show treat him like a “hysterical” woman. Because Scully is rational TO A FAULT. And her brother still has never taken her concerns, ESPECIALLY about her own body and health seriously. And when she is simply describing her experience he immediately puts her in the “spooky” category. This woman doing DNA analysis is basically the same as a man screaming about UFOs.
Which is one of the reasons why MSR is so great. They respect each other in this deep and profound way. They care about how the other one thinks. They can come to different conclusions but trust each other so deeply. And as an audience member is really seems like this is not a respect Scully has been afforded in her whole life!