There is no question that pedophiles operate very freely on the web. My own research over the years has time and time again found pedophiles openly sharing images and making contacts on Flickr. Flickr clearly does almost nothing to break up the networks of adult men who repeatedly favourite images of young girls playing at pools or beaches.
I personally am concerned about witch hunts, but the level of pedophile activity on the web and the unwillingness of major companies and governments to do anything about it probably makes what Anonymous is doing necessary.
Probably only a mass exposure of pedophile sites and networks via a mass event like this can do anything. It is extremely difficult to counter specific users one at a time.