The assumption "their terminal values are fixed to hate group X" is something akin to "this group is not human, but aliens with an arbitrary set of values that happen to mostly coincide with traditional human values, but with one exception." Which is not terribly different from "These alien race enjoys creativity and cleverness and love and other human values... but also eats babies."

Discussion of human morality only makes sense when you're talking about humans. Yes, arbitrary groups X and Y may, left to their own devices, find it rational to do all kinds of things we find heinous, but then you're moving away from morality and into straight up game theory.