In the beginning it was "Think of children". In my country they drived throw illegal censorship (Our constitution denies censorship). They claimed it would be overseen, etc... It wold only effect servers not in our country..
Today its used for much more then just what it was originally intended. It censors sites critical to to this censorship system, it censors pirate sites (not even claimed to distribute child related material), etc...
Censorship is such a dangerous road. Once you take the first step, its so easy to take another and then another and then another.... Until you are light year away from what was originally intended.
Theres no oversight of system. List is classified, Who manages that list is classified, and theres no court oversight of it. So if you are wrongly places on censor list, theres no way to get out. It volantery system for ISP to be part of, except if you dont implement it volantery theres law we can make it...
Personally i believe its problem of democracy. Too many old folks on power that dont understand modern world. They think sweeping problem under the rug is doing something, because that seemed to work in past. Child related issues will not go away if you put them under the rug, you need to take action... Unfortunately censorship is the wrong choice of action. Smoke and mirror trick that leaves problem un-handled..