I think it has something to do with a failure to appreciate humor:
Humor as a psychological defense mechanism is considered one of the most mature and effective. Sigmund Freud himself, suggested that of all the defenses, "humor is the highest." George Vaillant, in his book The Wisdom of the Ego, states that, "The mechanism of humor is defense so subtle and so elegant that words fail."
Basically, humor permits the overt expression of feelings without individual discomfort or immobilization, and simultaneously without unpleasant effect on others. It allows people to face the most painful reality-- and yet respond almost playfully to that reality.
Humor requires maturity. It is a creative adaptation to sometimes a dangerous and frightening world. At its best, it is an expression of hope when the unbearable must be born. Most often, very young children are not able to appreciate the healthiest kind of humor simply because they are too young and their egos too fragile to be able to enjoy the self-deprecation and subtlety.
To quote the creators of South Park, responding to Comedy Central censorship:
" So, Scientology, you may have won THIS battle, but the million-year war for earth has just begun! Temporarily anozinizing our episode will NOT stop us from keeping Thetans forever trapped in your pitiful man-bodies. Curses and drat! You have obstructed us for now, but your feeble bid to save humanity will fail! Hail Xenu!!!
- Trey Parker and Matt Stone, servants of the dark lord Xenu."
FULL DISCLOSURE: I am not actually a big fan of South Park, but I get all rebellious and annoyed when I am told authoritatively that I am not allowed to do something like read a certain book; watch a certain TV show; or say certain things. It is one of those little psychological foibles I have about free speech and all.
- Dr. Sanity, servant of the Lords of Light and Lady Liberty