Churchill was a devious old bugger.
I wouldn't underestimate his cunning in making remarks about Australia..
Remember he was a man of war, not peace.
I recently read a biography by an American on him; very interesting, a man of paradoxes. He certainly was a man of war; he seemed to thrive on it and derived his best and worst moments while knee deep in it. Once he got an idea in his head, it was impossible for him to shake it. On the other hand, his general staff were constantly having to put up with his constantly changing mind on certain aspects of the war.
John Curtin raised his ire with a speech he made to the Australian people declaring the nation's loyalty to the USA with Australia's declaration of war on Japan, which was a sensible thing to do - the NZ Prime Minister had cemented relations with the USA before Pearl Harbour. Churchill was angered by Curtin's declarations, even FDR stated he was panicking. Nevertheless the speech pretty much let everyone know that the country was going into a wartime footing. He was a man who didn't mince his words at a time when Australia needed men who didn't mince their words.