But then Aussies did nothing when Howard banned semi-autos in 96.

Imagine the response if Trump did the same?
His head on a pike would decorate the smouldering ruins of the White House.
It's like Americans have more respect for the Office; while Australians show affection or contempt for the individual who holds the office.
This might stem from the idea that our Head of state is actually the Queen, and the PM is more of a high ranking public servant.