Yup, pretty messed up stuff. You can find a few other country's censorship lists on Wikileaks, and invariably they end up blocking more than just child porn websites. Thailand's, for example, blocks a number of sites that are critical of the government. The potential for abuse is too great.
I wouldn't so much be against filtering if the block list was publicly available or there was some other form of oversight (I mean I still wouldn't like it, but this would at least make it somewhat palatable), but having some super secret list with absolutely no oversight... not a chance in hell I could support that.
Fortunately, it sounds like the Australian content filter has been stopped (for the time being, at least).