The githyanki are racist because they view everyone who is not them as lesser, this is literally what Laezel says in some of her dialogue, "our lessers", and because their supremacist society is based on raiding and killing others. So I really don't follow your own logic here, because most races are in this setting are not like that.
The closest comparison would be drow following Lloth, who also leave the Underdark to raid and kill. And indeed are feared on the surface because of that, which is a reaction you will sometimes get when playing a drow. Githyanki are simply less known, so most people in Faerun don't recognize them for what they are, e.g. one if the tiefling kids asking a githyanki if they are a swamp elf. But if you play a character that is familiar with them, then there is no reason to trust Laezel.
