This whole argument is somewhat silly. Oskar seems to have picked "fitness = ability to reproduce" as the hill to die on. However I really don't see anything in wuf's statements that disagrees with that.

If I understand wuf correctly, he's simply saying that there are biological/evolutionary benefits when people identify with a particular race/ethnicity that is different from someone else's race/ethnicity. Those benefits can be amplified if people organize themselves into societies and systems of ideas along those ethnic lines.

wuf was also clear to state that too much of this is just as bad as none of this.