RE: Sesame Street, the rainbow angle, and… Monsters (commonly known as pedophiles)
Ok, so we know about the Bert and Srnie thing.
Here's something else to consider:
Monsters… are equated with both grotesque animals and grotesquely evil humans in popular dictinaries:
https://www.merriam-webster.com/dictionary/monster (def #1b)
https://www.dictionary.com/browse/monster (def #3)
Now, How much of a coincidence is it that Sesame Street equates playing with monsters as… Fun?