I think it's because Microsoft's reason for doing this is plausible and not as anti-competitive as that comment makes it seem - locking down the boot process has serious security benefits.
If it's openable it's not locked down. If I can't trust the kernel then every level above it is tainted (this is assuming you can trust the CPU and firmware, but at least ARM is better than Intel here).
OK, let me be more accurate: "user-openable" in the sense that the user is free to choose to trust any OS vendor they want. What's the unmitigatable harm?
A user that isn't the owner of the device - say a repair tech, but possibly a remote third party - installs an OS they trust, which scrapes all the device owners personal info and sends it to their server. The device owner may not ever become aware of this.
"Others do it too" is not a good justification of course. But his comment also fails to to explain how Microsoft is somehow more evil than the industry standard.
Bootloader lockdown was practically unheard of for the PC/laptop form factor before Microsoft started doing it for ARM laptops. And and it's not even really standard for phones. Plenty of Android phones have unlockable bootloaders (see LineageOS).
I don't think whether one is more evil than Apple/iOS in this regard is a good benchmark.
Lockdown of consumer grade devices isn't really a new experience (e.g. iOS devices).
There's a trade-off to be had between security/reliability and flexibility.
If MS were selling those devices as general purpose computers and then refusing to allow other OS installation, I think that would be dishonest, however as far as I'm aware they're not making such claims.
I don't see the tradeoff honestly. Sure, make it a little difficult, show a big red scary warning, perhaps even require the use of a screwdriver to discourage "casual" users from being misled into compromising their machine's security.
But ultimately true ownership, recyclability/reusability (Linux on aging hardware..), and hardware-independent OS competition are norms with significant benefits that we shouldn't give up lightly.
Those may be norms for IT professionals, but the needs of IT professionals are very different from those of standard users.
Realistically most people (numerically) don't want a computer, they want a thing that lets them communicate, create and consume content.
Lockdown isn't a problem for them, and walled gardens like iOS are generally the best way for them to stay secure.
If you provide a method to escape the sandbox, it is likely that attackers will work out how to exploit that. For example try going to facebook.com and open the developers tools. They've had to put a warning in there to stop people from "self-XSS" ...
That's why I'm entirely OK with making it scary and a little difficult.
And it's not just IT professionals, but also their friends and family, especially those that can't afford to or don't want to get a new device that often. I think this is a pretty significant set of people.
So are you not ok with the concept that some people don't need that option and, as long as the vendor is clear about what is and isn't possible, having some devices that are more locked down that others is acceptable?
If I knew that to be the end-game and if I knew it to be an informed choice on the part of consumers, yes, I'd be OK with that.
My two reservations:
1. I think such a lockdown is a kind of hidden anti-competitive "dark pattern" that benefits the seller much more than it benefits the consumer by significantly lowering the the reuse/resale value of the device. One could argue it makes the device cheaper to begin with, but I have serious doubts about that. The anti-competitive effect seems more likely to increase the price instead. Hindering reuse also implies an environmental impact, though I'm not sure how significant that is.
2. If lockdown becomes the norm for >99% of devices/users and even we tech people start to accept it the way of things, some sufficiently bribed lawmakers will no doubt be inclined to make unsurveiled general purpose computing illegal because "security" and "copyright" and "pro-business" etc. Yes, it's a "slipper slope" argument, but when it comes to social norms, I think that's a valid form of argument.