Well, the OP presents an interesting hypothesis I've never heard before!
I always thought clowns, throughout time, have always been part of societies as a way of commenting on and bringing to awareness our less conscious
behaviors and contradictions, as individuals and a collective.
Just as comedians today do (George Carlin, for example...), the jester had the ability to show a king his own mistakes and foolishness in a way that
could "get in the backdoor" as I tend to consider it - humor, poetry, music, dance and body language can sometimes bypass the conscious awareness,
allowing messages to be stimulated to arise from the unconscious.
We laugh at a silly behavior or joke, but later it slowly dawns on us that it is ourselves who are the fools.
The jester is a mirror of our shadow.
Seeing our faults and follies is sometimes hard, terrifying even. Imagine if you suddenly became aware one day that you had caused someone intense
anguish and trauma for the rest of ther lives... perhaps a loved one, your child, your parent, a lover. Many go through their whole lives not even
knowing they have done such a thing.
The day they find out they are the monster is a bad day indeed.
The clown that silently holds that up with a dance and a stumble, a gesture and a horn, can make you giggle at first, until the message sinks in
Ultimately growth, healing and change isn't possible without such realizations. We need clowns - as individuals and as a society. We need the artists
that find indirect ways to bring our shadows back to us.
When you mature, you sometimes become more adept at owning your weaknesses and faults, facing them and dealing with them, so the clown seems like less
of a threat.
I think that was also the point Stephen King meant to bring about in the ending of his book, IT, which I found distasteful when I read it (did they
include that in the movie this time???) . If you know what I am talking about, I think he meant to illustrate the transformation from child to adult,
the integration and bringing together of YIn and Yang (darkness and light, shadow and the ego...).
While at the same time, poking at our cultures foolish taboos about sex .... I am painfully aware of that when I realize how much it troubled me and
how I am not even writing clearly what that scene was!
What a clown, that Stephen!