Just like they can always make the argument that they are protecting people with xyz questionable tactics, you can always make the claim that something on the Internet is for the purposes of free speech. That doesn't make you right, or even mean that free speech is the primary legal or moral distinguishing factor even if you are.
While it might be uncontroversial, some people would still prefer if the state used effective and evidence-based methods to prevent child abuse, rather than using ineffective, costly, and what ever method that get most media attention.
For example, mandating that schools has trained counsels at staff is a prime example in identifying and preventing child abuse. Having a trained expert which kids, parents and teachers can go to is important line of defense. New teachers should also receive basic training when studying at the university, so they can detect psychological, emotional, social, and physical signs of abuse.
Current studied methods in creating effective prevention program also includes group-based sexual abuse prevention education for children (http://www.princeton.edu/futureofchildren/publications/docs/...). Sadly, the efforts in creating more effective prevention efforts is sadly somewhat low priority (see linked document).
It should also be noted, that in that whole document, more strict Internet regulation is not mentioned at all as effective prevention method. Feel free to speculate widely why the researchers did not mention it.
Then they do some old fashioned police work, and you get cynical responses like yours. They didn't warrantlessly wiretap anyone, or violate anyone's rights, to take down someone who was knowingly breaking a horrific law.