It is said that…some types of cancer are so painful that the amounts of morphine to dull or eliminate the pain would kill the patient with an overdose. At some point it is said that some people weary of the suffering, and would welcome death as release from the physical agony…of slowly dieing a most painful death. If the patient does not want to live…I can understand their choice. Dieing is a natural part of life, and extraordinary beyond the pale methods to sustain “life” go against the grain.
The following is from the Catechism:
scborromeo.org/ccc/p3s2c2a5.htm#I
2278 Discontinuing medical procedures that are burdensome, dangerous, extraordinary, or disproportionate to the expected outcome can be legitimate; it is the refusal of “over-zealous” treatment. Here one does not will to cause death; one’s inability to impede it is merely accepted. The decisions should be made by the patient if he is competent and able or, if not, by those legally entitled to act for the patient, whose reasonable will and legitimate interests must always be respected.
Further:
2279 Even if death is thought imminent, the ordinary care owed to a sick person cannot be legitimately interrupted. The use of painkillers to alleviate the sufferings of the dying, even at the risk of shortening their days, can be morally in conformity with human dignity if death is not willed as either an end or a means, but only foreseen and tolerated as inevitable Palliative care is a special form of disinterested charity. As such it should be encouraged.
That above is the “Catholic Church Teaching” on the subject.
I have no problem either with the concept of “self-defense”.
But “putting down” humans because they are sick, old or infirm… I have great problems there. If it was legalized…if would only be a short reach to “put down” anyone with brown hair, freckles, green eyes, or whatever…