By the logic of most of the people posting here, if I publish a book and anyone chooses not to stock it in their store, I can claim censorship and take them to court. What if my book isn't any good? What if I'm trying to get my commentary on the Gospels into the Atheist book store? What if...
The right of the stores to sell the material that they deem appropriate is sacrosanct. Otherwise, all the bookstores are going to go down by being forced to keep lots of books in stock that they may sell once every 10 years. Is it "censorship" that WalMart refuses to carry graduate-level Mathematics texts? No, it's simple business. For better or worse, WalMart has determined that it is in their interests to provide only products that meet with a certain set of moral norms. This is primarily a business decision -- they presume that if they are selling CDs that parents will not approve of, the parents will not allow children to shop there, thus cutting their revenue.
Apple has to have the ability to decide what they sell, otherwise, by the Slashdot "all censorship is wrong" mentality, they would be forced to carry child pornography - Nazi - Holocaust denial - Terrorism howto software, and then be shut down by the government. And the decision of what they choose to sell or not sell must rest with the company, otherwise we can't hold the company responsible for what they sell.
It is another thing if the government steps in and says that a particular piece of software cannot be sold anywhere. That's why we have a special name for this practice. The common usage of "censorship" to apply to anyone who chooses not to distribute material for any reason, cited in the parent post, essentially makes the term useless. We need to expand our vocabulary. WalMart doesn't "censor" artists, but rather "bowdlerizes" them.