Sure. That's my personal approach on gnolls, for example, that the 5E demon origin is just cultist propaganda. My orcs aren't inherently evil or destructive either, Gruumsh is just one story. But that's just my preference, of course.
So mind flayers, that in many senses behave and react like a person, and are clearly intelligent beings, are OK not to treat as people because they don't look human? Because we're told they're aberrations?
Conversely, if you had a species that looked human, but ate brains, reproduced through tadpoles, and had strange psionic powers, would it be OK to treat them as inhuman? What if they had the humanoid type instead of aberration?
If you can't treat them as inhuman, why? Aesthetics? Looking human is the dividing line? But 5E gnolls don't look human, or even act human; the only clear indicator of their being humanoid is their type. They could easily be defined as monstrosities. Or even fiends. But officially, they're humanoid.
If it would be justifiable to treat this hypothetical human-illithid as inhuman, why are 5E orcs different, if they were created by Gruumsh to pillage and destroy, and it really is part of their nature? What if Wizards had decided orcs in 5E were monstrosities instead? Or fiends? Would they still be problematic?
I don't mean to put you specifically on the spot, to be clear. And I'm not advocating that Wizards shouldn't address obviously problematic things in their products. But I'm just trying to illustrate that these lines aren't as straightforward as some folks might think they are. Especially to folks not familiar with D&D, unlike most of us on ENWorld.