Sadly, I don't think that all people are treated alike in Australia, as the grim accounts of the detention centres indicate. There is also deep-seated racism towards the Aboriginal people, which is a bit ironic as they were the original inhabitants! Obviously, not all Australians are racist - far from it - but it is hardly a shining light as far as the immigration issue is concerned.
Regarding the question of whether there would have been a similar outcry if Remain had won, there are two things to consider. One is that people who oppose the EU have hardly been reticent about their opinions in the past and I doubt they would have been in the future. The second, and more important, point is that a Remain vote would have been a vote for the status quo. Nothing would have changed, and we would still have the opportunity to change our minds at any time in the future. However, the Leave vote means major changes, with serious implications for our standard of living, our role in world politics and the possibility of future divisions - and maybe conflict - in Europe. In addition, there is no way back, once the process begins. Of course the Remainers are agitated, because there seems every possibility that the future changes will be largely negative and we can't change our minds, unless every other country in the EU agrees to take us back.