Apple should be allowed to block whatever they want from their app store. And users should be allowed to run whatever software they wish on their devices not installed through Apple's store.
Although, I think it would be better to just not install any browser by default and not even ask; you can install it yourself later if you wish to do so, and can install any one you want (or more than one, if you wish) instead of having to pick one from the provided list.
*or company. Perhaps part of the answer is that sometimes we say yes for people but no for companies.
Of course, this is the domain of contract law. Often car companies restrict how soon a desirable model can be resold and for how much.
edit: And robust anti trust enforcement keeps contract terms reasonable. Contracts are limited by unconscionability and superseded by legislation but otherwise fair game.
You state that "Apple should allowed [sic] to block apps from third party app stores on devices they paid for". No mention of users or owners rights post purchase. Did you mean "should not be"?
But long thread about nothing, I was just trying to clear up the misunderstanding.