Even the Christians realise that internet filtering is not going to protect kids. The very conservative Christianity Canada has a piece in which it is pointed out that no filtering is a substitute for parental oversight and education. Meanwhile, Crikey again notes that the proponents of mandatory internet filtering are the Christian Right. Why is the ALP, a left wing social democrat party, trying to suck up to them? I suspect the answer is wider than mere partisan loyalties. Governments hate things they cannot control, as witness the fact that the NSA in America eavesdrops on ordinary American's electronic communications with no oversight whatsoever. I suspect the ALP just likes centralised controls, and internet filtering is a useful pretext to expand that way. And while the current opposition parties are against it, weakly, they once did put up a proposal themselves.
The real evil for governments and would-be governments is that there are things happening in their societies they don't control. Governments hate that. Bureaucrats hate not managing these events and politicians hate what a free media might do to them. It's much harder to appease an entire populace than a single newspaper proprietor. So they demonise the internet by making it all about child porn. I have been using the internet for various things since the early 80s, and in that time I have once found a child porn site by accident. I have as much chance of stumbling over bad porn electronically as I do physically in someone's trash.