Been thinking along similar lines.
Basically, a synth produces a sine wave, square wave, or saw wave in most cases at the basis (whether for electronic drum sounds, melodic sounds etc.)
Now, perfect sine waves don't occur in nature, but all natural waveforms can theoretically be decomposed into sine waves (mathematically), i.e. these are sort of the "building blocks" of sound, interacting with each other in complex ways (like many different ripples on water producing patterns).
This means that using pure sine waves to create sound is sort of an artificial "deconstruction" and focusses accoustic power sort of one-dimensionally.
Perhaps a good analogy is how a laser works: normally, light is very complex as seen in nature, and it can be beautiful, like when you watch a sunrise. Now a laser takes a very small part of the spectrum and focuses it in a powerful beam - which can do great harm to the body. I mean, in laser surgery it is literally used to burn and decompose flesh, so there you go...
Similarly, a sine wave is an artificial powerful acoustic "beam" that doesn't really carry information, but just raw energy, which I suppose can bypass the body's natural state of being "tuned to the natural acoustic environment" and do harm.
Also note that if a pure sinewave as a building block is one end, noise is the other end (per Grok:)
So the world of natural sound exists on a spectrum between a pure sine wave on one end and white noise at the other - both of which are very unpleasant to the ear: a pure sine wave is like a needle piercing the body, and white noise is like crashing into a wall. Beauty, creativity, and pleasant sound lie between those extremes in infinite perturbations.
Now, this could mean that if the synthesizer sound is heavily filtered, modulated etc., which it almost always is, this could make it less bad, since this introduces overtones, distortions etc., making the sound more "natural" (it's also more pleasing to the ear as a consequence). But the problem still remains that these sounds are built on an "unnatural" foundation, and parts of the negative consequences remain - you can still hear these basic "deconstructed" artificial waveforms in there.
"Anti-human" in this context means that here in 3D we live in a natural, "human" acoustic environment that carries information produced by processes that generate complex patterns to which we are attuned. Brute-forcing artificial sounds that use the "raw building blocks" into our environment introduces an "alien element" that "pierces" our natural human attunement, and is therefore "anti-human".
Some more on the math by Grok: