>If the actions and beliefs of a group are fundamentally morally repugnant to me,

sure, although if tribal differences are always experienced as fundamentally morally repugnant one might think the moral calibration is screwed a bit too tight.

>I think that it is reasonable to not expect me to be able to find "something positive" in it.

Sure, I do think it is possible that some groups are so morally repugnant that they have absolutely nothing to offer whatsoever. For example that tribe of cave dwelling cannibals in the film The 13th Warrior, man those guys sucked! But the comment seemed more to be about how it is weird that when you find some group does some things that you find morally repugnant then they have nothing they do that can ever be good.

I have lived in places in which I find much of the surrounding culture to have behaviors that I found morally repugnant, or intellectually repugnant for that matter, but even at my most contemptuous of a culture and a people I will at times be forced to admit, honestly, that they have behaviors that can also be considered admirable (in many cultures the repugnant bits are so tightly bound to the admirable bits though I can see how it is difficult not to condemn everything)