First off, game talk. When it comes to Mind Flayers, you ABSOLUTELY can stereotype them as completely evil abominations deserving nothing but death for being unrepentantly malicious in their every action, and say that of every member. Because they're literally a race of hive mind parasites. There's only ONE exception to this rule, and that's a guy who made a potion to essentially reverse lobotomize himself before his tadpole turned his head into a squid, effectively preventing it from overwriting his personality, and forcing him to live permanently undercover.

Second. Wow, how tone deaf can you be? Berating someone as being racist against entirely fictional creatures, and then turning around to slag the entire country of Germany?

What a POS you seem to be, lad, if you are spewing out such balderdash.
Shame on you and shut up.

I haven't played BG3 yet myself (I'm waiting for the final release before doing so as I have a very low tolerance for buggy/unpolished games and I want my first taste of BG3 to be as awesome as possible), but as a long-time D&D player I figure I'll just add in my 2 cents about this.

While it's not IMPOSSIBLE for there to be a Good illithid, it would be extremely, microscopically rare. For starters, a newborn illithid is not like, say, a freshly turned Vampire. There is NOTHING left of the original person in the new illithid; their brain has been completely consumed, and nothing remains of their old brain, personality or memories. Even their soul is no longer there, having moved on to the Outer Planes at the moment the tadpole consumes the last of their brain. As such, there is no way for the previous victim's personality to influence the new one.

Secondly, the illithids have a hive mind and are all connected telepathically to the Elder Brain at all times (unless they move too far away from the community, but the Elder Brain does not allow "young" illithids to leave the community unless it is satisfied that they are a) completely loyal, and b) capable of defending themselves. Constant telepathic exposure to the Elder Brain means that any illithid would rapidly be indoctrinated and grow up thinking it is completely normal to view non-illithids as nothing more than cattle, useful only as food and slaves, nothing more. (And if the illithid somehow rejects these views, odds are good the Elder Brain would have the offender culled as a flawed mutant.)

Finally, illithids MUST consume living brains from sapient humanoids in order to survive. The longer they go without eating fresh brains, the weaker they become and eventually die. This requirement means that, on some level, they will always regard humanoids as being "food animals". Even the most detached illithid philosopher would probably keep some intellectual distance between himself and any humanoid scholarly associates he might have, if only because it's helpful not to get too close to a creature you might one day have to eat.

All these factors taken together means that the odds of there being a Good-aligned illithid who actively enjoys and prefers the company of humanoids to his own kind being infinitesimally small. The only way I could conceive of it happening is if there happened to be an illithid who was "born", but was then somehow removed from the illithid community and grew up without any instruction or influence from the Elder Brain at all (and even so, Factor #3 would still be a grave challenge for them fitting into any humanoid community), or alternatively, if some kind of powerful magic was used to change their alignment. (But again, Factor #3 and the fact that any other illithids or the Elder Brain would detect the illithid's new alignment and dispel the magic quickly means that option 2 is not likely to be a permanent situation.)

I did not turn around anything, quite the opposite. I have strong connections and lots of friends from Germany and I haven't met a single German so far that I can call racist. Especially after he kept his racist comments for blaming me for being leftist and spreading hate for the west. He was the one who tried to associate me with the terrorist attacks, which was a racist comment on its own.

Racism is racism, in every culture, region, fiction or not. It is called racism whether it is against elves, droves, or illithids. Just because some people can not comprehend that does not change this fact. Racism is not a subject for FUN. Also, implementing racism in games just to make it more realistic (like The Witchers series for example) is DEFINITELY NOT the same as supporting those ideas yourselves.

Shame on me for despising racism on all possible platforms.

yes all these points are in the game

Not necessarily humanoids, but sapient creatures, they consume the lingering psionic energy and that is what they actually need from the brains, not the physical matter, even though they derive nourishment from that as well.
Back in 3.5e their minds are explained as being almost Dalek-like, only being driven by negative emotions and viewing all other creatures as slaves/food, but having an obsession with understanding and science.

I don't know how 4e and 5e have changed their lore since there is no equivalent to the Lords of Madness book in later installments, but since DnD is supposed to be flexible to individual DMs I don't see a problem with it as long as they explain it with a backstory.

TBH I still don't understand why an Illithid, perhaps a rogue spellcaster looking for the secret of lichdom couldn't join up with a band of adventurers. As Astarion says, there's going to be plenty of evil stuff to kill and none of those are going to need their brains after they are done with them anyhow...

There are a few Lich Illithid about, the result of the more magically inclined being given too much leash in their mystical pursuits. They're about as bad as the living ones, just more passive in their destruction of all life for their own enrichment. As for rogues in general, they're exceedingly rare since, as mentioned before, Mind Flayers are a hive mind existence. Every thought is broadcast across the hive to every other Illithid and the big evil brain they worship. So, if one got the idea that it was going to run off, it'd be met by the full psychic might of the entire hive. And even then, IF it managed to escape, no sane adventurers of any race would even consider letting one join up. And even if it psychically or magically disguised itself, sooner or later that will fail. And even barring ALL that, a rogue Illithid would be easy prey for the Githyanki, even with a party of adventurers backing it up.

Unless something happened to cut it off from the hivemind. A traumatic brain injury, for example - the Illithid version of becoming deaf and mute, suddenly severed from the linkage to it's brethren and, for perhaps the first time since ceremorphosis, forced to actually think for itself ...

That sort of thing should be extremely uncommon. For one to then turn to Good, or at least Neutrality, should be even more vanishingly rare.

But it's not quite impossible ... :)

Yeah, I'll give ya that. Granted, the circumstances listed could just as easily drive it irrevocably mad. Granted, it'd still be left marked for death forever from that from a thousand directions.

I don't know about them being marked for death if they got disconnected and went rogue. The hive mind would just assume that it got killed. The only way it would know if the illithid was still alive is if they encountered it. And astral space is infinite.

.... becoming "nice", and changing to a good alignment, pretty much would fit the Illithid definition of "driven irrevocably mad", don't you agree? :D

No. Because doing things out of insanity actually precludes one from being Good, and in many cases from being Evil. Doing things out of insanity makes one Chaotic Neutral. Acts of Good or Evil require a certain amount of clarity, which a broken mind, no matter how powerful, simply isn't capable of.

Not only do I reject this with every fiber of my being as nonsense .... It' actually more than a little bit insulting, as it clearly suggests that someone with mental health issues cannot be a good person. No everyone who is insane, would necessarily be chaotically aligned, let alone Neutral rather than Good or Evil.

In the real world, no, of course not, that'd be absolutely ridiculous. But in D&D, it's true, as subtle shades of grey simply aren't a thing there. And they're not a thing because D&D is about clearly defined forces to facilitate pulp style heroics. Someone who is "mentally ill" in D&D isn't mildly unbalanced, they're a gibbering wreck, like they just saw Cthulhu. Someone who is Evil isn't just suppressing the commoners and embezzling taxes, they're having pregnant women thrown off castle walls and sending bandits after their own people to divert attention from them because they're just that cruel. And the reason it's like that is simple. The real world is depressing enough, dealing realistically in game with deep and complex issues with no right answers, while it may make for a good story, is ultimately misery inducing and only serves to drag you back into the real world, which a lot of people play D&D to get a reprieve from.