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173.37.1.145
Since: Dec, 1969
Chariset
Since: Jan, 2001

You have two groups of people who are separated by differences that to an outside, objective observer are totally arbitrary (e.g. one group is red, the other blue), but which both groups are convinced opposes them entirely and eternally, even though they're really identical. It's a parody of partisanship and group identity.
I'm specifically trying to remember a specific literary/proverbial example of "black x and white x," where x is some nonsense name that isn't coming to me. It's driving me nuts.