As others have mentioned, the idea that "freedom of speech" is a concept originating from and specific to the US Constitution is staggeringly ignorant, and the idea that freedom of speech can only be infringed by the government is too.
Freedom is about what the less powerful can do even when opposed by the more powerful. Money is one of the rawest forms of power in the modern world, and so if someone threatens to decrease your income significantly unless you change what you say, they are unambiguously flexing their power at you and impinging on your freedom of speech.
Any previous customer of mine that doesn't continue to buy and wear my T-shirts filled with "obscenities" are denying me my freedom of speech by threatening my income (since I've set myself up as a T-shirt merchant); they are built into my forecast projections as repeatable sales, and they are not allowed to not deal with me.
1. There is a difference between not buying and demanding change. If I demand that you stop selling obscene t-shirts, or threaten to stop buying any of your t-shirts, I'm infringing your freedom of speech.
2. I don't see where anybody said that Citi shouldn't be allowed to do what they did. But that doesn't change it from being a form of censorship.
There is no difference if the consequence of failing to meet the demand is the demander not buying, or not doing business anymore. It is just stating the conditions for continued relationship ahead of time, and providing an alternative course of action. How harshly would the bank be judged if they simply dissociated and gave the blogger no option to adjust?
The fact that the blogger is continuing to blog as he sees fit counters any objectively verifiable assertion that censorship was involved.
I believe the term censorship is best left for those situation when a state agency (which one might be able to argue many large banks are anymore) demands changes or cessation of communication under pain (or threat) of fine, imprisonment, or death.
Freedom is about what the less powerful can do even when opposed by the more powerful. Money is one of the rawest forms of power in the modern world, and so if someone threatens to decrease your income significantly unless you change what you say, they are unambiguously flexing their power at you and impinging on your freedom of speech.