Diversity is just a statistic, it's neither good or bad in either direction.
Not all forms of diversity is strength.
Mixing a wolf with a bunch of sheep isn't diversity, it's dinner time.
Racial purity ain't all it's heil'd up to be either: https://www.nature.com/articles/s41598-019-38571-1 https://www.newscientist.com/article/2342731-neanderthal-fam...
Have a barbie, find some middle ground: https://www.youtube.com/watch?v=yGdj1TwBU1w
Inbreeding in small populations (your first two links) is not relevant, and your third link is a false equivalence.
One extreme counters another extreme, the point is that neither are relevant, the third link is there for fans of The Bell Curve.
At least you'll admit that your ideas are extreme. That false equivalence does nothing to rebut the bell curve.