Be it limiting "appropriate content" or filtering news sources, I think there should be a line between the device/OS vendor and their ability to "curate" the world view of their users.
This is about Apple not selling the Daily Mail in their newsstand, not about them not allowing the Daily Mail in the iOS App Store.
I think Apple should be allowed to do the former. Certainly, they should be allowed to block some content from there, shouldn’t they?