For anyone who's read the Drizzt novels, it's pretty well established that the people of the Forgotten Realms freak out when they see someone who looks like a monster (see the reactions to Drizzt). It's quite jarring that Tieflings are seen as anything but KOS monsters. Based on those books, you'd never even start a conversation with one. You'd just shoot the Tiefling on sight from long range (or flee).
The books are informed by the D&D lore, but they aren't canon.
It just seems like a strange contradiction if you came to the FR via the novels.
Totally agree that any PC race will be normalized. But I do think it at least warrants an explanation when BG3 sets up red-horned devils as actual devils from hell. A few lines of dialogue from Lae'zel when you first encounter the Tieflings at her cage would work. (Or she could say something in the Prologue if the PC is a Tiefling) It's a fairly easy problem to address and it makes the story feel more realistic instead of hand-waving a glaring plot hole.
The Drizzt novels are set about 150, maybe 200 years prior to the current time line. In that time, the drow and tieflings have become much more well known as people. The Sundering that happened during 4e STILL happened and that increased the number of things like Dragonborn and Tieflings. Also there were a ton of drow that were re-welcomed by the elven gods, hence the existence of Seldarine drow and they are now a significant and open minority on the surface.
Also, tieflings never had the kill on sight reactions that drow did. They were a bit distrusted and in small communities may get run out of town, but there's not a history of tieflings coming in the night to kill and raid for slaves as happens with drow, so much less immediate fear to tieflings than with drow due to the fact that most people know of a place where Lloth-sworn drow performed some atrocity.
So many tieflings in one place would make people suspicious though....and that's probably why they have their own refugee caravan and aren't with all the other Eltrugard refugees.
The latest Drizzt Novel (Relentless) take place during 1488.
Descent to Avernus campaign takes place in 1494. (Which means BG3 takes place just after the events of Descent to Avernus)
Neverwinter Nights 2, takes place around 1374. One of your companions was Neeshka, a Tiefling from Neverwinter.
In Thay, many thousands of Tieflings were slaves, and then around 1377 Szass Tam took over, driving many Tieflings into becoming refugees.
Netheril Empire returned from the Shadowfel in 1372.
Spell Plague happened in 1385, Neverwinter got blown up in 1451 after adventurers woke the Primordial in Gauntlgrym.
Basically, there's an untold number of Tieflings spread across the region from a number of different cultures. There would be traveling caravans of Tieflings just roaming Faerun looking for trade, adventurers, small villages that may have formed because other cities/villages didn't want them. (In the Drizzt novels, we start seeing "Halfling" villages pop up because of alit the height-ists in Faerun.)
The Tieflings we meet, coming from Avernus is very suspicious, and given the context of Baldur's Gate, it doesn't surprise me that we'd have to choose between "Lawful Evil" and "Chaotic Evil".
If anything I'm surprised they're allowing other Tiefling bloodlines when the Lore specifically states that Asmodeus literally screwed all Tieflings over by changing their bloodlines... Also speaks volumes that the ending to "Avernus" they went with, may not be the "Best" outcome, as there is still a Zariel bloodline.
