Dr. Blockhead: Nature abhors normality. It can’t go for long without creating a mutant. Do you know why?
Scully: No, why?
Dr. Blockhead: I don’t know either. It’s a mystery. Maybe some mysteries are never meant to be solved.

(Incidentally, this is the first hit when you search “x-files humbug,” and it’s exactly the scene I was looking for.)

UPDATE 2019-05-29: This is no longer the first hit when you search “x-files humbug,” but it is the first hit for “x-files abnormal.”