Many European and Asian airlines have done tags in Australia, Thai also was operating BNE-SYD-BKK not that long ago.
Maybe but they were carrying passengers BNE-BKK not letting them off in SYD.
As for the argument "its only north of the tropic of Capricorn'. This is 2015 not 1942 and the Germans/Japanese lost the war. North of the tropic of Capricorn is thankfully still part of Australia. Australian airlines are under enough pressure without this b*llsh*t.