I'm not sure how not being differential is supposed to work though. Different groups have different kinds of failure modes.
Suppose it's actually true in the world that all people are irrational, that blue-eyed people (BEPs) are irrational in a blue way, green-eyed-people (GEPs) are irrational in a green way, and green and blue irrationality can be clearly and meaningfully distinguished from one another.
Now consider two groups, G1 and G2. G1 often discusses both blue and green irrationality. G2 often discusses blue irrationality and rarely discuss green irrationality. The groups are otherwise indistinguishable.
How would you talk about the difference between G1 and G2? (Or would you talk about it at all?)
For my own part, I'm comfortable saying that G2 differentially negatively characterizes BEPs more than G1 does. That said, I acknowledge that one could certainly argue that in fact G1 differentially negatively characterizes BEPs just as much as G2 does, because it discusses blue and green irrationality differently, so if you have a better suggestion for how to talk about it I'm listening.
What if G1=BEP and G2=GEP and discussing outgroup irrationality is much easier than discussing ingroup irrationality? Now suppose G1 is significantly larger than G2, and perhaps even that discussing G1 is more relevant to G2 winning* and discussing G2 is more relevant to G1 winning. How is the situation going to look like for a member of G2 who's visiting G1? How about if you mix the groups a bit? Is it wrong?
if you have a better suggestion for how to talk about it I'm listening.
You connotationally implied the behaviour you described to be wrong. Can you denotationally do that?
*rationality is winning
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.