I don't see anything in "Some Conclusions" to imply that differences in the complexity of folksongs are due to innate differences in human nature. Sharp underestimated the sophistication and level of material development of Aboriginal culture, as did almost all whites until recent times: if you think people are leading an existence of early-Palaeolithic unsophistication, that alone would give you the idea that they had music to match.

The attitude Sharp expresses has been just as repressive, though. If you think Aboriginal culture is so backward it can't produce anything of great sophistication, the obvious fix is to eradicate that culture. Which is what the forced resettlement and adoption schemes of the 20th century tried to do; the underlying assumption was that Aboriginal human nature was fine if you just brought them up white. Subtle (cultural) racism ended up being even more destructive than crude (physiological) racism.