A) You seem to hold doctors in very low esteem, equating them with paid hit men.
B) You refuse to allow a terminal patient the ability to manage his own demise.
I really wouldn't wish upon you the experience of a terminally ill relative begging for relief from pain and the indignities associated with not being allowed to die. (Yes, they revived him even with a written DNR order.)
Seeing as though doctors have shown their willingness to rip unborn babies to bits, it's not a stretch to believe that there will be doctors who might shoot up somebody's grandma with poison.
I regard doctors as I do all people, corrupt and tending towards evil. If evil is profitable, then men will arise to do it. The way to keep this manageable is to ensure that the temptation does not arise. This is the problem in the Catholic church placing sexually active homosexuals in the clergy, and allowing them to associate with young men. The results were inevitable. I do not regard doctors as being of a higher moral caliber than men of the cloth. If we make it legal for doctors to kill essentially anyone they want, and there are people who will profit from these deaths, then killing people for profit will become an active branch of 'medicine'.
Legalized abortion was also supposed to relieve the desparate victims of rape, incest, botched alley abortionists, etc. To make the human experience less tragic.
Has it done so? 30 years later we have abortion at whim, for any reason at any stage of gestation, up to and including the moment of birth. We have the barbaric practice of Partial birth abortion, the main purpose of which is not to convenience the woman, but to provide intact fetal organs and tissues for the rapacious "medical" research community.
Abortion has become a billion dollar industry that operates hand in glove with the "sex educators" who encourage sex because they are dependent upon the known failure rate of contraceptives to provide new clients and fresh parts for their abortion mills.
Euthanasia will be no different, moved by horror stories of affliction and despair, the sheeple will buy into these "mercy" laws for legalized killing, and another death industry will be spawned. Only the ages of the victims will have changed.