You're right, it is a type of censorship. But, in this very small, minuscule and completely irrelevant context it is a subject I'm willing to have censored. There is no real comparison between having a genuine opinion worth hearing and, I quote, "OMG ESCHER!!1!!SHIFT1!!" That post was made with the sole intention of harassing the seller, who was indeed selling a rare prototype model Apple and while the outrageous costs some ebay sellers demand are just plain stupid, the fact that they never sell and they never learn is evidence enough that its not going to change.
If there was genuine interest in the item and contact had been made and the seller turned out to be an ass, then warning the community to not buy from them is prudent, but simply flaming them because you can is little more than a childish use of an ignorant interpretation of free speech.