I have to admit that my first reaction to this was that the person sending the e-mail had misunderstood the cartoon. It seemed to me to be actually pro-Indigenous, using typical ironic white Australian humour to highlight the injustice of the British land grab. I too would have had a little chuckle and kept reading.
As I thought about it, though, I realised a couple of things. Firstly, the person who sent the e-mail was not a white Australian and therefore might not share that sense of irony (I was being eurocentric!). The second was that since I wasn't one of the people whose land got invaded, it didn't really matter what I thought. An Indigenous person was clearly offended by the cartoon, and I'm assuming she wasn't alone since the list moderator sent the message on.
This made me think about the difference between being accidentially offensive, and being deliberately so. In this case there is no doubt that the cartoon is offensive since Indigenous people were offended. Whether the cartoonist meant to give offence is another matter. I doubt that he did. He just didn't know enough about Indigenous culture to know what would give offence. Neither did I.
It reminded me of a quote from "Murder in the Collective" by Barbara Wilson. One of the characters says, "...you worry about being called racist as if it were syphilis or something. Like you were accused of having some dread, disfiguring, incurable disease. But I think it's more like telling someone or being told, 'Hey, you've got snot hanging out of your nose.' You say thank you and wipe it off. Though that doesn't mean the snot's not going to ever drip again."
So, I've just wiped the snot from my nose and I hope the Courier-Mail cartoonist can wipe his too.