The tieflings I met are just a lot of poor people with horns.
And that is exactly what the problem is. They are not, or the very least they are not supposed to be "just ordinary people with horns". They are an entirely different species. This over humanization of them is exactly what destroys the importance of race in this game. Elves are just humans with pointy ears, halflings are just short humans, dwarves are just miner-vikings etc. This is not a good thing. Races should be radically different, and simply making them LOOK different is utterly meaningless. It's like reducing someone to how they look on the outside. Race should carry more meaning than that, especially in a medieval setting where mass literacy and education isn't a thing, so people can't be expected to know that they don't stand face to face with an actual devil (because let's face it they look like devils, they are related to devils, and assuming that they are just like you is absolutely unfounded). If you want to sell me on the idea that tieflings are "just people", then make them a subrace of humans, otherwise I'm not interested in continuing this discussion.
These are fine points, the question is how you deal with them. You could go head against the wall and say "I don't care about the game narrative tieflings are supposed to be evil so I'll kill them all" or you can address the ones we actually got in the game, not some hypothetical ones.
I don't know much about tieflings outside of video games, but my assumption is that there are some good some neutral and some bad. You know what, even if most of them are evil, unless it's like 90 percent I don't think the attitude of "kill them all" makes any sense, in universe and otherwise. It doesn't mean you can't create a good written character that believe it is the right choice, but I can't see supposed character as anything other than a misguided at best and villain at worst.
