This makes sense to some extent (terminal illness or such), but one can argue as someone did above that if you're willing to make the permanent decision to "destroy" yourself, are you sane enough to legally make decision? Are you for sure not under temporary delusion, distress, or other threat? You can always "legally" "destroy" yourself through suicide, but if you want to involve a medical professional it seems very reasonable that you have the mental clarity to make the decision.
Should it be illegal for the doctor to deny me an amputation that I ask for? After all, I should be "free to destroy myself" absent any justification?
> You can always "legally" "destroy" yourself through suicide
Not in a dignified, foolproof way. E.g. can you go to a pharmacy and get a dose of morphine that will kill you with certainty? You can't, in most jurisdictions.
Forcing other people to deal with the trauma of cleaning up your bloody remains after you jump off a window isn't exactly compassionate either.
Give people a clean way out, even if you don't want it for yourself.
Should it be illegal for the doctor to deny me an amputation that I ask for? After all, I should be "free to destroy myself" absent any justification?