I don't find Stephen King to be that much of a cerebral writer. He's a quantity over quality kinda guy and with the amount he's written it's almost inevitable to come upon a great number of gems. As far as I know he's the one that created the whole genre of "innocent childish thing is actually evil". It was literally a million dollar idea. Serial killers mumbling nursery rhymes, killer dolls, child ghosts, devil kids, haunted schools, cursed toys, masked Halloween killers, evil crazy parents, dream monsters, evil siblings, and so on are horror-movie themes that are being constantly recycled even now. A killer clown is just another subset of that same idea.
The underlying message of "adult cover-up of child abuse" does seem to me to fit however take in account that the clown is actually not a clown, or a human, or a demon, but a giant spider. Why? Because some people have a phobia of spiders so wooooo, scaaaawry.
A better movie that does have an underlying message is The Babadook. The movie takes on a whole new meaning (removing the supernatural element altogether) when you realize the first half is from the mother's perspective and the second half is from the child's perspective.
That said I would love to hear more movie reviews from Stefan and Mike. The District 9 review was also fantastic.