> You cannot argue on principle that diversity is a good thing while simultaneously arguing that it can be a bad thing. This is an obvious contradiction.

Moderation (in the sense of temperance) as a meta-ethical principle has an exceedingly long pedigree, starting with Aristotle in the Nicomachean Ethics. Every virtue he describes is a mean between two extremes; courage lies between cowardice and recklessness, for example.

TL;DR: Every virtue has a “oops you went too far” failure mode, this doesn’t make it “self-contradictory”.