Just after I put up my previous post with the response from Christopher Pyne, @Tarale on Twitter made me aware of this great response to Senator Conroy from Simon Hackett of Internode. He concludes:

Either way, given the facts I have noted here, it is clear that mandatory URL level web page filtering actually harms society (through a false sense of security) and has no positive impact.

There is no justification for the path that the government is pursuing, none at all.