Wikileaks is sitting on a ton of info about the ADF's war crimes as well, and the Australian government want nothing more than to prevent the intense scrutiny of its proud fighting force by the worlds' people that would result from such a leak. They are fighting tooth and nail to ensure that Wikileaks is invalidated completely in the minds of the Australian public, who generally have very little temerity when it comes to criticism of their armed forces actions.

EDIT: Besides which, there is Australia's heinous Sedition law, which is being floated as the means by which Assange would be silenced were he to land back in Australias territory.