That's all very fair, but I think what people are taking exception to is Apple's attempts to prevent their customers from accessing other content distribution platforms where Apple doesn't get a cut.
Why should they not be allowed to generate revenue from someone who is using all of their technology and network distribution work to make their own money?
I think you are missing the point here, as an example, Amazon cannot sell ebooks in its own site if it's cheaper than the version in app store, if so they remove it from app store. Apple is trying to control pricing outside of its distribution network. That's what I understand from the whole story.