But this is exactly what makes it hard to abuse. With oddly-moralized hackers up in arms, you can bet they'll seize on any abuses of the filter and plaster them embarresingly over the internet. So the government has a strong incentive to stick within their declared uses of the filter.
So the worst objection to the filter is simply that it could mostly be a waste of time... that said, it will evolve and change and may prove useful.
You don't want to wait that happen. Eventually the government will become having a face so thick that they just outright lying to the citizens. China has already set the example, and I surely you don't follow the shit.
http://zh.wikipedia.org/zh-hans/%E8%BA%B2%E8%B2%93%E8%B2%93_(%E7%B6%B2%E8%B7%AF%E7%94%A8%E8%AA%9E)
In 2009, a 24yo Man died while being detained. In the press release, official stated that the suspect died from head trauma by hitting the wall when playing hide-and-seek.
http://news.mylegist.com/1604/2010-03-01/21338.html
Two months ago, another man died while being detained. This time the reason given were he drank too much water - despite that there was a hole in the head, nipple and gential showed signs of abuse.
I am picking the two most obvious and well-known cases, there are many more unbelievable cases like that happening frequently. Although for both cases, the department in a higher hierarchy later came up and clarify the truth. But nevertheless, IMHO they crossed the line. Yet the Chinese couldn't really do anything besides chatting about it on the net. There is no way to replace the official, the government or the party without bleeding.
Going back to Australia and the other countries, you don't want to let your country to step out the first step - please defense your rights.
The "think of the children" is pointless, the child molester will find their way to get the actionable material no matter what, you think a filter or two will stop them? They are driven by the sexual desire and nothing can stop that - human is just another animal. Nor the filter could cure them either. Just like lock can only keep honest people honest - Internet filter in the national sense could only make your Internet experience more trouble, not those child molesters.
Once the government wins this, they will take a even more aggressive step and when you finally find out it's outright unacceptable - it will be too late - and welcome to join the Chinese.
Exercise your right while you still have it, and please protect it, treasure it.
Disclaimer: I'm a Hongkonger, but living in Shanghai.