EDIT: Thank you for your response, dang. Hacker News is a special place, which is why we have responded so strongly to today's events - I apologize if the tone above came off as less-than-civil. I (and it seems, many others) look forward to hearing more about the 'dupe' article others have linked to below. It was only upon seeing the article marked as a dupe after seeing the previous flagged out of existence that it began to feel like more than just a user-initiated action, so I am sure further information on the mod-initiated actions will put these fears to rest.
You must have a remarkably selective definition of free speech then. Stuff gets flagged all the time, and users are suppressed via opaque and obfuscated methods.
To be clear, I'm not saying that moderation is a bad thing. But increasingly I notice that people use the term "free speech" to simply mean "speech I agree with".