Tieflings have no leanings towards evil in this edition. But it is correct that the common populace *does* look at them with great suspicion and for all they know, a tiefling might be an actual devil.
How a character reacts to a Tiefling should depend on their moral nature and how much they know about the nature of devils and Tieflings. Unfortunately, BG3 currently does a poor job of introducing you to the dilemma - and an even worse job of telling you about the preceding events surrounding Elturel.
This makes sense, I'm sure there's Tiefling racism stemming from their infernal ancestry, but I'm not sure there's going to be any society that they're not common enough in that the kind of attitude Eldath is advocating would be considered sanctioned, Innkeepers might refuse them service, sure, but the killing one on sight, I'm not so sure.
We've seen this already in BG:3 the Tiefling refugees were all residents of Elturel that the city exiled after their misadventure in Avernus. Though the particulars are still unclear. And you'll notice that Elturel didn't just kill them all.
