Why would it diminish, unless you're presuming special reasons for racism to revive there?
Why did racial goodwill in the Northern US diminish after the civil war? There were a goodly number of reasons, but foremost was once the South was included in the political discourse again, race-baiting became tolerable. And the Republicans backed down after a decade or so of defending the black man, deciding to embrace capital instead, so the racial situation continued to worsen through the early 20th century.
I see a similar issue here. It will be tempered, however, because there is no overwhelmingly white (well, few) parts of the DSA that can just ignore the race issue to maintain their own political base. Of course, I don't recall Glen saying what the electorate was in the DSA - it seems a tad bit early yet for universal male suffrage, so if there are any qualifications to voting blacks will be a small enough group of the electorate to safely ignore.
Many were slave owners but I think the Indians tended to accept newcomers adopted into the tribe regardless of their origins.
True enough - many tribes were highly mixed. Given situations like this, and the upper-class mixed-race creoles in Louisiana, I think you'd see more of a Latin-American style gradated racial hierarchy than a strict color line. But it would still be pretty bad for most black DSAers regardless
Rational people can fairly easily tell them apart but if you're used to thinking of a black skin as a sign of inferiority at best it's going to make it more difficult for any black settlers from the DSA.
Again, I just don't think so. Aborigines are going to live at the edges of settlement, or in the wilds, or in miserable poverty. DSA blacks are going to speak English, dress like everyone else, and have roughly the same material conditions as whites.
Not to mention once the Australian colonies get representative government they could also introduce a 'white Australia' policy as OTL.
But this is supposing that non-whites don't play a role in settling Australia prior to responsible government. Also "white Australia" was meant to exclude Chinese and other Asians. Other non-whites weren't even excluded at all until 1895, and even then NSW, Tasmania, and South Australia excluded "undesirable persons" of all races rather than formally limiting immigration to whites. The British government was unhappy, but Joseph Chamberlain said
"We quite sympathise with the determination...of these colonies...that there should not be an influx of people alien in civilisation, alien in religion, alien in customs, whose influx, moreover, would seriously interfere with the legitimate rights of the existing labouring population." I don't think they'd take the same attitude towards excluding nonwhite, but culturally British, subjects of the crown.
To a degree but then they might be lumped in with the existing black population. Also, small groups are vulnerable when the community feels the desire to lash out about something. If only small numbers emigrate to Australia there might not be a strong racial reaction, especially from the authorities but if only a few come it won't make a big difference to the DSA either and it sounded like people were speculating on a fairly large scale immigration from the DSA.
My point was the ball could get rolling rather innocuously. After that, it's a roll of the dice whether the local authorities will clamp down on immigration. But I think it's fairly feasible that given so many less whites will be coming to Australia ITTL, they will continue to not be particularly choosy so long as someone speaks English and is Christian.
I'm not saying those factors will stop it totally or deter all black immigrants but that it is likely to make their numbers fairly insignificant because they will prefer the DSA or possibly the US.
I think the most likely happenstance would be a "sable" population in the range of 5% (assuming no barriers, but also no subsidies or settlement movements), but depending upon the course of Australian history, I could see as low as a 1%-2%, or as high as 15%-20%.
However if there are significant problems for the blacks in the DSA or simply the US starts to develop as rapidly as OTL then it will attract a lot of settlers and you have a group just over a fairly open border who have the same language and some aspects of a common culture. As such, unless the DSA expands enough to keep the bulk of it's population there could be a significant number until an increase in racism and/or legislation restricts it. [Which I agree reverses my initial argument as I was assuming a greater degree of hostility to setters from the DSA, especially those of a darker skin
].
Then we're in broad agreement here.