Hmm. I'm not sure it's accurate to call it censorship. A business has the right to decide what products it wishes to carry. As long as there are alternative markets for the product, it can still get distributed. For instance, I wouldn't want to see X-rated comics sold on the rack at Toys R Us, but I would want their publishers to be able to sell them through other, age-appropriate markets. It would only become a problem if Toys R Us were the only business that sold comics at all. Then its marketing decisions would become de facto censorship due to the lack of alternative channels.
So defining this as a censorship issue is missing the more basic problem, which is monopolistic business practices. The problem isn't that Apple is intentionally restricting free speech; the problem is that Apple is too much of a monopoly and is thus restricting free trade, with free speech being a casualty. What we need is to break up the monopoly, restore the antitrust laws to the strength they used to have.