'Slow and painful manner' is factually wrong as they gave them medicine which eased the symptoms. I don't like the word evil but I would greatly enjoy to shove it back into the throat of a hypocrite like Burke who opposed the French Revolution.
Episodes like Dear Doctor and Cogenitor are Prime Directive episodes. They show the genesis of this concept during humankind's first steps in space. A principle does not have to be codified yet to be active. I don't have to point out via previous Prime Directive episodes that even before the supposed wickedness of Archer and Phlox the Prime Directive has been the very opposite of Burke's stupid aphorism, do I?
Anyway, this discussion has arrived at a dead end. You disagree with the the Federation's main principle while I am a proponent of it. I won't call you a Cardassian though and I found the difference between our standpoints, my cold ethics and your warm compassion, interesting.