Maybe they genuinely believe people shouldn't duplicate their functionality, and that they should try to innovate on their own?
I guess it's fine when they do it, but not when others do it to them.
Except MS has already been held responsible for their actions (from over 10 years ago), and all indications are that the company has changed drastically for the better in the past few years - stability- and security-wise.
Meanwhile, Apple is trying to drive all their competitors out of business not by putting out better products and competing on merit, but by abusing the legal system due to their vast cash reserves with ridiculous "rounded corner rectangle" design patents.
MS did some bad stuff a long time ago. They have paid for it (literally), and they are no longer the same company they were back then. Apple is doing bad stuff right now, yet all indications are that for the next 20 years we'll still be constantly reminded of Microsoft's already-paid-for behaviour from the 90s, but Apple will still be lauded as a magical untouchable company despite their unpaid-for behaviour from today.
Your analogies are quite ridiculous, and have nothing to do with the topic at hand.
That's one of the points of requiring that ARM win8 tablets are not allowed to disable secure boot. If MS subsidizes ARM tablets to drive sales, they don't want people buying cheap tablets in order to install another OS at their (literal) expense.
The implementation allows for the installation of other operating systems but only if they've been signed by a MS key (well, any key, but the only ones that will be installed on a win8 ARM tablet will be MS's). They'll be able to charge for that signing process, and recover their subsidy in that way.
The other point is that since the only way to put new software on an ARM win8 tablet is via the app store, they want to ensure that intercepting the boot sequence to install an exploit that bypasses or interferes with the app store is blocked by requiring that the entire boot chain is trusted.
Whether they get it right is yet to be seen, but those are the reasons.
Except that Metro on WOA will run the exact same binaries that Metro on Win8 x86/x64 will (except for those few that use native code).
Windows, as a platform, probably has a larger base of developers than both iOS and Android, and anyone publishing a Metro app to the new Windows App Store will have it available to WOA users automatically.
So, assuming that developers start making use of the beta that's coming out end of this month and start writing apps to target Win8's new Metro interface, without even knowing or caring about WOA, this will mean that WOA will have a decent enough supply of software at launch.