A website that does not allow you to post x is not infringing your freedom of speech in the context of the first amendment because that only stops the government from censoring you, and doesn't stop individuals from censoring others nor does it force individuals to perpetuate others speech (as in host it).
But it is most certainly censoring you on their website. That is almost exactly the definition of censorship. It would be exactly the definition of censorship if you posted X, and then they removed said post. If they have a blanket ban on X prior to any such post, that can still be considered censorship. And hey man, some censorship is good:
-Self-censorship is best. I'm not going to wave my dick about on a playground. That'd be pretty fucked up. And illegal. And rightfully so.
-Outlawing any discussion of global warming, anywhere, online or off, would be a crazy-stupid level of censorship. And illegal.
-StackOverflow censors any open-ended discussions, because it's a Q&A site striving for quality posts rather than bickering about which language to use. And I'm down with that.
But news aggregators like Fark and Slashdot where the "value added content" is the community and commentary, I prefer the censors to have a light touch. If someone is being a real douche, sure, ban'em. But I'd be worried about mods becoming tyrants. And from the sounds of it, I'm glad I'm not a regular on Fark anymore.
You are allowed to say whatever you want "within reason aka slander, fraud, and so on" you have no right to say it everywhere.
Correct. Just like I said in my post. It's great we agree. But that sure as shit doesn't mean that Fark's new policy isn't censorship.
(Also, and I'm just being pedantic here, you DO have the right to say it, but they also have the right to ban you/kick you out of their store/house/server. Effectively, no you don't have the right to say it everywhere)
Remember, what rights you have is a legal quandary. The act of censorship, which is the anti-thesis of freedom of speech, is not tied to legal matters. If you want to sue/arrest someone, consult the law books. If you want to uphold the ideals of freedom of speech, you need not consult the law.