I really wish someone in the know would reply to your post because I think you have the most salient point. In fact, do the same open source advocates decry the Playstation and Nintendo platforms?
PS3 is a very good example IMO. It comes with very powerful hardware, which you paid for, but you are only limited to rules placed by sony. As a matter of fact Sony goes through a lot of trouble to make it almost imposible to do anything else with the hardware.
Similarly, I should be able to install any app on my iphone/ipad that is not approved by Apple without have to go through hoops of cracking the device.
Have you been following the kerfuffle behind Other OS yankage?