If anything this bizarre attitude that literature "may be the only way to gain an actual comprehension of human nature" might be an artifice of people's desire for success and prestige--puffery motivated by a personal insecurity about the significance of one's interests or work. You want to gain an actual comprehension of human nature? Read history. Go to the bar. Have some kids. Sit down on the curb and talk to a homeless person. Travel. Put yourself in extreme situations with other people (like joining the military or something). You'll learn a hell of a lot more that way than by reading novels.