To me it's not solely about modification. It's also about transparency. While I most likely would shy away from trying to modify the software of a medical device, I think it should be illegal to lock down those devices so that people can't at least see the code that's running it.

If you're going to build something that's going to directly affect my health, I would much appreciate it if it were easy for researchers to find bugs and security issues with the software that controls it.

But ultimately I don't care about the whole "legally locked down" thing, and think that concept is a net negative for society. If I can buy a medical device to use at home, then it should be on me if I decide to modify it and it injures or kills me. I expect the law hasn't really kept up with that notion; I wouldn't be surprised that in many cases the manufacturer might still be liable. But that's a legal problem (that should be fixed!), not an ideological one.

> ... or a payment terminal the user is explicitly not trusted to modify

This is the worst thing, IMO. I wholeheartedly reject the concept of software that I am given to use, but am not "trusted" to modify. Screw that. Unfortunately I do have to use software like that. But I think the entire concept is garbage.