I think the jump from unreasonable to immoral is rather larger than you seem to imply.
A better analogy would be a car company that forced you to come to them for all of your service and for any after-market work you wanted to do.
Perhaps Apple is more mercurial and arbitrary. But the institutional arrogance is the same.
As a manufacturer, Wal-Mart is your best friend and worst enemy. They pay you promptly and order lots of stuff. But they demand steep discounts and punish you harshly if you fail to meet commitments, and you must be able to rapidly ramp up your supply chain when their demand grows.
The only thing you can really argue is that they should allow other app stores to exist that aren't under their control. And frankly, they do exist on jailbroken phones and if you want that you can jailbreak your phone, or get an Android.