What a cute way of denying the spiritual universe and by implication of denying the spiritual component of evil, also denying God. For if humans are the only monsters (evil) existent and we only identify humans as the problem, then the solution becomes simplified to eliminating the human monsters among us to resolve said problem. If humans can resolve our own problems in this way, there is no need or room for God much less salvation from the sacrifice and resurrection of Jesus. The Bible speaks against this dangerous naivety in Ephesians 6:12.

For we do not wrestle against flesh and blood, but against the rulers, against the authorities, against the cosmic powers over this present darkness, against the spiritual forces of evil in the heavenly places.

Yes, there are real human monsters. The (self identified) elite of the group very much are actively in the service of Satan and his demons. We may be seeing the elite humans as the monsters, but there is a greater spiritual unseen evil even more monstrous than we perceive the human monsters to be. It is here that your meme denies the spiritual reality in our world. By denying the spiritual evil that seeks to destroy all men by using man against man, the statement is false and seeks to diminish human awareness of the spiritual realities we live within.

In this way, I would argue that Scooby-Doo as a show subtly tries to persuade impressionable children that all things spiritual are just silliness and parlor tricks by setting up straw men stories of cartoon human bad guys trying to scare everyone by dressing up as ghosts as if that were how the spiritual realm functioned.

Also in my book you can add Casper and other similar cartoons and shows to the list of media that tries to diminish the realities of the spiritual realm by creating straw man type stories that deny or minimize the existence of the spiritual world.