Australia is not the only country to have politicians who go out of their way to be rude to The Queen, it seems. When the Deputy Prime Minister of Canada questioned the role of The Queen just as she was about to arrive in Canada in 2006, this triggered the following debate on Canadian TV.
Perhaps the major difference between Australia and Canada on this issue is the proximity of the United States.
Note that the objection by the republican in this debate is not constitutional or to monarchy as such, but to the fact that the monarchy is multicultural and global, and that it is shared with 16 countries.
This does seem to be a very old fashioned, rather antiquated, view of the world – and from such a young man.