A favorite analogy of mine:
Say you have a bucket, and in that bucket you have tennis balls and baseballs. Definitionally, it is diverse. This is very useful if you want to play baseball and tennis, but if you only want to play either baseball or tennis, the bucket becomes less functional. If, on the other hand, you wish to play golf, the entire bucket is useless.
Diversity, despite the modern feeling, is most certainly not a virtue in itself, and it does not add intrinsic value to a thing and more than, say, its size (a large pile of gold is very valuable, a larger pile of feces, on the other hand, is not). I would actually argue that excessive diversity can be detrimental to a society — I don't know about you, but I am glad that the paranoia of the 1950's is over, as well as the violence of the early unionization movements.
Even if we lay aside questions as to whether humans have intrinsic self-worth (over and above other life forms) (as a warning, I do not make that assumption but rather the opposite), there are still problems present in Nazism. Here are two which come to mind immediately, the first to do with the National Socialist internal policies, and the other to do with external policies:
- First, the choice of who to eliminate was arbitrary (remove people who happened to share a certain ancestry and ideological output) included some who were decidedly beneficial to both the economy and society as a whole (doctors, professionals, musicians, etc).
- Second, the Nazi idea of lebensraum meant the forceful subjugation of surrounding (read: all) nations, by force.
Both of these trends are destructive in the sense that they did active injury to others and thereby undermined the implied social contracts which must necessarily exist for the continued function of society. If lebensraum were to be taken on an individual basis, then I would be well within my rights to go out and start forcing my neighbors out of their homes. If society were to take the opinion that money should be given out arbitrarily without respect for any sense of talent, then that will actively remove creativity as a virtue.