I think the hostage taker is a white convert. At least that is what I could make out of the images of his released.
With that said, Australia is very much influenced by the UK, particularly Abbott's right wing government. Just like the Afghans in Pakistan pump Pakistani Pashtuns to hate Punjabis and Sindhis, the bagpackers and immigrants from UK pump the local aussies to dislike the muslims and "not make the mistakes that England made". I have witnessed this phenomenon a number of times.
As for the "England's mistake", they themselves invited uneducated mirpuri Pakistanis for cheap, menial jobs, and are themselves responsible for their radicalization. The English formed unprovoked skinhead gangs in the 80s, after which the whole muslim community got radicalized. Although I'm generalizing a bit.