We should be able to install what we want on a general purpose computing device. You can already see the Apple mentality creeping into other companies like Mozilla, who suddenly find it acceptable to limit user freedom for questionable reasons, and the normalization of stripped user liberties that Apple champions is worrying.
But similarly, there's no law requiring anyone to sell products that allow you to do whatever you want with them once they've been bought.
You can argue for such a law, but competition law is a pretty weak place to start.
Arguably, Apple is creating a market by their policies: the fact that it's not filled with competitors indicates only that most people don't care.
Either we do, in which case what Apple is doing in perfectly reasonable, as is Walmart selling fridges that explode when you put someone else's milk in them ("It's in the contract!"), or it isn't.
Things like the first sale doctrine give an insight into past legal thinking suggesting the latter. But it's far from simple to discern by just looking at the law.
The music/video industry asserts that you're not allowed to play/show some media item that you've bought. Amazon doesn't allow you to resell or bequeath Kindle books. Caterpillar doesn't let you repair your own tractor.
The first sale doctrine was established in a very different time.