The thing that makes it more complex is that they are preventing you from (legally) using a boob app on their device at all, which is much more serious.
EDIT: These applications don't seem to have been blocked from the UK AppStore. Well we are less prudish about these things.
Wrong. The U.S. Constitution demands the U.S. Government allow citizens the right to free speech. It doesn't require non-government entities to do so, however. It's why a bar can eject you for telling a cocktail waitress she looks hot. Please don't argue with me on this -- I passed the Bar and you apparently don't really understand the basics of the U.S. Constitution.