Easy answer to your question -- do a quick google search for NAMBLA
We don't censor the opinion that people should be able to have sex with children.
There is a very clear line and it's called the First Amendment.
We censor child porn because it is a crime that involves a victim.
The Daily Stormer was all talk.
Once you start talking about censoring people who might cause people to commit crimes, you've crossed a philosophical boundary into policing thought crimes.