Anyway, I think you can have freedom of speech and moderation. I don't think it's a violation of freedom of speech to have certain areas dedicated to specific topics, in which off-topic posts get removed. As long as all speech has somewhere it can be posted (e.g. by allowing users to create their own sub-forums where they decide the rules for themselves).
Eh, the bans are trivial to get around unless you have a static IP, you have to really spam to get a rangeban or rangerestrict (e.g. can't make threads) and the common "moderator" is literally called a janitor and routinely mocked across all boards. Disdain for moderation is one of the core tenants of the site culture.
For instance one of the (board specific) rules of /int/ is to respect other cultures and people but half the (non-general) threads are either blatant bait or arguing about how other people in country/region X cannot suffer.
Further reading: 4chan.