Blocking sites with illegal content can be done without destroying freedom of speech.
No, it's impossible. Once a government starts to censor a certain type of illegal content, the censorship will soon expand to include every other type of illegal content as well (warez, hacking tools, bombing construction manuals, all porn sites without youth restrictions,) followed by content considered harmful (islamistic and nazi propaganda, governmental uncontrolled gambling, information about drugs) and sooner or later include every website the current government doesn't like for any reason whatsoever (discussing loopholes in law, sharing speed camera locations, oppositional opinions.) This will happen because "the government has to protect it's people by all means possible" and once new possibilities are clearly available, they have to be applied due to political pressure.
Of course, in Germany, censorship is actually unconstitutional. It's not a coincidence that it starts with childporn even though it probably only represents a very small fraction of all illegal websites. It's the one subject nobody can argue against without commiting political suicide. Nazi- and antisemite stuff will certainly follow next, opening the door for everything else.
The fact that these kind of extensive cuts to people's right of 'freedom of speech' is currently happening all the world, for many unrelated different reasons no less, should be alarming.
"Truth never comes into the world but like a bastard, to the ignominy of him that brought her birth." -- Milton