Websites that publish child sexual exploitation material are getting heavily censored in the U.S. too. Think through what uncensorable implies.
To me, it implies that things you agree with and things you don't agree with cannot be censored. This seems like a prerequisite for a free society.
I found the reference to hate groups to be a much more effective argument, I think purely because everybody is so used to the kids/drugs/terror angle being overused and abused to chip away at liberties.
Surveillance-state dystopians take note.