In this speech, Keating makes two basic assumptions.
The first assumption is perhaps the most important -- that the actions of white Australians are to blame for the historical and current plight of the aboriginals. Keating assumes that the problems of the aboriginals were caused not by some fault or faults of their own but rather by the abuses committed by Europeans. As Keating says:
We took the traditional lands and smashed the traditional way of life. We brought the disasters. The alcohol. We committed the murders. We took the children from their mothers. We practised discrimination and exclusion.
The second assumption is that these abuses were committed because whites did not see the basic humanity of aboriginals. Keating argues that whites could never have done these things if they had understood that aboriginals were people like them who had feelings like them. This is why he repeatedly invites white Australians to imagine how they would feel if the wrongs done to aboriginals had been done to them instead. To quote Keating again:
It was our ignorance and our prejudice. And our failure to imagine these things being done to us. With some noble exceptions, we failed to make the most basic human response and enter into their hearts and minds. We failed to ask - how would I feel if this were done to me?
From these quotes, we can see that Keating assumes that the plight of aboriginals was caused by whites because they failed to see the basic humanity of the aboriginals.