If, in addition to the App Store, developers were able to distribute apps themselves, there would be no problem. People would grumble whenever Apple introduced another asinine policy, but there wouldn't be such an outcry. Some restrictions in return for extra visibility and use of Apple's distribution system is a fair trade.
This isn't what we have though. It isn't just Apple's store they're locking down, it's the whole device. A store that you can't freely put software on is unfortunate but understandable. A computer that you can't freely put software on is just wrong.