Shit. I have to admit he has a point.  Seconded. Even if all his examples were taken from thin air (and while I am not familiar with a lot of them, I do not think that; He seems to have been quite diligent), his point still stands: Grouping up is human nature. Hell, sorting all manner of stuff into neat groups is a huge part of our long-term civilization.  But with this desire-to-group come downsides as well, one of them being in-group bias, and with it, playing down the shortcomings of "your own". It's always easy to see if you have a distance to the matter the bias lies in, but if it's part of something you are personally engaged in, bias can be very hard to see.