The will of the people is the true purpose of democracy. Regardless of the fact that people are doing this anonymously, this is similar in line to the rebellion against a tyrannical government.
Just because the tyranny is not as bad (censorship of porn), and the attack by the people (DDoSing government websites) does not make it a "joke" or an immature prank.
If the government was actively rounding up thousands of people from a certain ethnic group for "cleansing", you could expect everyone to gather guns to kill them.
Since it is not that serious, you get a less serious, albeit effective response. It made them realize what the public wants.
And I don't believe this is a symptom of the "vocal minority" simply because people don't get involved with something for no financial gain, unless they genuinely believe in it, and while it could be the act of a few, it is most likely the act of many.
Even if it were a vocal minority, in the US, the constitution was created to protect the freedom of the minority. I don't know how Australia views it's minorities, but I would hope a country that everyone considers "western" holds the same ideal.
Anonymous is the true unhindered will of the people. It does not give in to socially acceptable norms, or anything that hides what someone truly wants.
If people want porn, they will do so under anonymous.
Anonymous is legion.