Who says that? People, myself included, don't want specific harmful for society groups to be allowed to speak free, not that nobody's allowed to say anything.
Yes, nazis should not be allowed to speak free. And no ramblings about privacy here on HN will ever change my mind.
In fact, I'd be happy to sacrifice my own privacy if we can root out the evil of racism, nazism, terrorism, and other things that absolutely everybody agrees are bad.
That being said, I think the frameworks used to prevent that at the moment have a lot of potential for abuse, especially from private companies. And it's something that should be improved upon, and normal people should have privacy as much as possible.