When you go to the dentist, the dentist takes control of your mouth and forces it to do what they want. I don't see what's confusing about that.

If you think the scope of the loss of control doesn't line up: replace "brushing your teeth" with "watching your blood pressure"; "a toothache" with "a stroke"; "the dentist" with "an ICU doctor"; and "taking control of your mouth" with "taking control of your whole body" (since you're likely under general anesthesia — they've literally taken control of your body away from you to fix the problem.)

But, by looking at my analogy as analogizing two fields, I think you missed the point. I was trying to give a general analogy about preventative maintenance tasks you are expected to enact as part of the ownership of a tool; where that tool will eventually 'randomly' break down without said maintenance, effectively forcibly interrupting you to have reactive maintenance done by some external professional at much greater time cost. Your teeth are just one such tool.

A different but equivalent analogy would be to changing the oil in your car. If you don't do it, eventually at some 'random' time you'll need to spend a long time at a repair shop because your engine cylinders got grit in them and wore holes large enough to lose stroke pressure.

Also, if you mean to suggest that these cases are different because the computer is "choosing" to force the update on you, rather than "requiring" the update in some technical "being broken" sense — it's not like that's uncommon. Many tools and machines — industrial ones, specifically — come with resource and maintenance sensors built into them which will prevent you from operating the machine in a condition where it would begin to require maintenance, to prevent you from accidentally imposing an above-tolerance workload on a system that you presumably want to last a long time. Self-greasing CNC routers will stop running when they run out of grease, rather than trying to operate dry. Etc.

If you question why your system "requires maintenance" in the first place — well, this is what I addressed in a sibling comment. If you believe in vaccines, and in herd immunity; and if you understand that, for active threats (computer worms et al), computer networks have virality coefficients just like human populations do; then you should be able to see that the "maintenance" being required here, is for the sake of increasing the herd-immunity of the network by removing your node within it as a potential infection vector, rather than for the sake of your own computer's individual health per se. (Although it is also for the sake of your own computer, insofar as, besides just joining you to a botnet, a worm could also carry a crypto-locker payload or something equally nefarious.)

And if you question why Microsoft should be able to force your computer to "get vaccinated", when the government can't force you to do so — well, consider something the government can do: it can prevent you from driving a car that doesn't pass an EPA inspection. Because driving is a privilege, rather than a right. Well, operating your computer isn't a right either. It can come with conditions.

(If you, finally, notice that the distinction should actually be "operating your computer on the Internet", similar to "driving your car on the road" — such that operating your computer offline, or driving your car on a private track, shouldn't be something anyone other than you has a say in — well, I'm not going to argue with you there. Computers could certainly have the option to delay a forced restart to install a patch, but to "force you offline" until such time as the [already-downloaded] patch is installed. I think OSes only don't offer that because it'd be terribly confusing for the average grandmother. But it could certainly be something hidden in the most arcane of config flags.)