Continuity mistake: In the first footage of the episode we can see that the ambulance's lower right lamp is off. However, at the moment of the crash it is on. Not to mention that the Chevrolet logo, previously seen at the ambulance front, has vanished. We conclude it is not the same vehicle. (00:00:10 - 00:01:06)
Continuity mistake: When Scully finds out about Betts' mother she says that "She lives right here in Pittsburgh." Nothing wrong there except that at the time they has just left Chuck Burks' lab - which is in Maryland. (00:17:40 - 00:21:10)
Factual error: When Scully is performing the autopsy on Leonard Betts' severed head, she states "As remains are incomplete, all observations refer to a decapitated head." This phrasing is redundant. The proper terminology would be "disembodied head." As a medical doctor, Scully should know this.
Answer: As he stated many times throughout the series, Mulder needed Scully to be sober and skeptical. Whenever Scully's skepticism wavered and she started questioning her own rationality, Mulder would try to restore her sense of skepticism, because he needed her to be clear-thinking.
Charles Austin Miller