The issue wasn't immigrants per se but the method by which they arrived. They were described as "queue jumpers", which plays against an ordinary australian's notion of fair play.
The numbers of legal immigrants (including refugees) are higher than ever but since the "stop the boats" policy, the number of "illegals" has been reduced to a trickle.
That was the rationalization. My understanding is that it was crafted to exclude non-white immigrants, like Trump's immigration policies or like election law in the U.S. south, which always works out to exclude non-white voters.
Also, it doesn't address the treatment of the refugees in the camps.
