Part of the issue, for me, is how unnecessarily often a character is boiled down to their race and not their actions or situation. For example, the druids in the grove are constantly talking about the problems with the "tieflings". Even if it isn't what they mean, it's hard to avoid hearing that the problem is that they are tieflings, at least a little bit. The druids never (or rarely, if I'm forgetting something) talk about the problems with the "refugees".
Do the refugees happen to be tieflings? Yes, but while that might be germane to why they are refugees, it is irrelevant to why they are a problem in this situation.
(Tangent: This situation would be a lot more interesting if one or more of the druids were tieflings. Also, if some of the refugees were not tieflings.)
Similarly, why have Lae'zel bother to call them "teethlings"? She thinks she's superior to everyone that isn't a gith - why is she singling tieflings out? (and with an insult that doesn't really make any sense - she's like a 7-year old calling names on the schoolyard).
Why are there a couple of humans living in the goblin camp? How did that come to pass? Why aren't there more? I want to hear that story.
To eliminate all racism from the game would be silly, but if you want to say something useful or interesting about it, you need to choose your moments. Have it say more about the person who is employing it than about the person who it is aimed at. Give players a variety of options to react to it (or not, if they so choose). If I want widespread racism without a point, I'll go for a walk - there's enough of it in the real world.
