Nothing should ever be blocked because a government says it should be. I don't care if it's a child porn site or a terrorist website recruiting people or a serial rapist sharing pictures of his victims. The moment you place that kind of power with the government there is no stopping it.
Besides, anyone who knows anything about the internet would know that the majority of high risk stuff, such as child pornography, is located in places where it can't be blocked or traced to begin with. The only thing ISP's are going to do is ban certain site addresses. Which is cute, but won't do jack shit. It certainly won't make a dent in any form of illegal activity. It only regulates what the general public is allowed to view. Which damn scary.