It's an ugly fact of human nature, and we see it manifest itself in other forms such as racism, intolerance to other social classes, genders, etc. However, in all these cases, it's the bigots that need to be reformed, not the victims.
Same exact thing with immigration.
As for the Nazi's, I simply meant that Nazis were intolerant of anyone who was unlike them. Cephus' response mirrored that intolerance by suggesting that everyone should conform to the American way. That the Nazis simply eliminated anyone who didn't conform whereas Cephus would like to forcefully integrate them matters little.... that would be like saying it's a poor analogy because the Nazi's spoke German and Americans don't.