Firstly, it implies there are differences between races, otherwise diversity and homogeneity would produce the same results. In the attempt to be non-racist MT has become racist. A common problem with Social Justice.
Secondly, the phase out of White Australia happened between 1949 - 1974 which correlates with the postwar boom (which was a global phenomena) and population growth, which can be achieved using any race combination. In short, MT has mixed correlation with causation.
Personally, I judge people based upon culture (which is learned and changeable by those willing), not genetics.
