How to create racial tensions without making "evil races"

What would be the right balance between "the bigots are right 98% of the time because this race is simply born evil so that 2% of the time they are wrong is in the margin of error" and "there is honestly no reason or excuse to be cautious or begrudging when dealing with other races and those engaging in discrimination are just being wildly irrational."

let's assume this is a fantasy world where the humans colonized every other race. Every other species has been assimilated into human society and beaten into submission so they won't resist on a large scale.

but that creates civil unrest, and these species still resist their mass human colonization, and even despise each other for their past conflicts!

Because of this resistance, the bigotry and discrimination feels completely understandable. Plus, the distrust sowed by this situation makes the species distrust each other, so it feels like they're not even TRYING to actually resist the human colonization!