Liam, I'm really confused about what you're saying.
You're acting as if people in Australia never get assaulted or need to defend themselves.
Statistics say otherwise, and so does my personal experience. I've had several friends in Australia that have been assaulted before, and one woman that was actually stabbed and almost killed by one of her ex husband's friends.
Maybe you live in a locality where those type of things don't happen, but apparently some people do.
I'm not arguing for or against carrying a gun there, but you seem a bit misinformed or idealistic as to how human beings in general are.
I think in most countries the probability of a violent crime happening to you depends on the region in which you live, but it is possible anywhere. Some people are idiots.