If someone is terminal and the person's organs start failing, the person's need for water will decrease substantially. In such cases, the need for hydration is correspondingly reduced, sometimes to basically nothing. Such a person might be adequately hydrated to live for a month without water were it not for the fact that the failure of the person's organs would kill them much sooner than that.
It is peaceful and more or less painless.
In cases where a patient's other organs are already shuttig down of natural causes, denial of food and sometimes water can indeed be painless. But for a patient whose organs are functionaing normally, the story will be far different.
It is a way of NATURAL death for people when the natural means of receiving food and water becomes impossible.
If Stephen Hawking's wife were to lock him in a closet for two weeks and he died of thirst, should that be viewed as death by natural causes or as homicide?
More specifically, in Terri Schiavo's situation, the feeding tube supplanted the natural means and made its withdrawal appear to be inhumane.
Had Terri's parents been allowed to make such efforts as they could to give Terri water and nutrition by mouth, that might have been 'humane'. Given that Terri was able to swallow over a liter of saliva per day, it would seem likely that she could have swallowed some water or nutritious liquid--administered slowly and carefully--were she permitted to.
Prolonging her life was inhumane and presuming man's means to prolong life more important than the way her body had already shut down YEARS ago.
Her body hadn't shut down. It was functioning jut fine as long as it was given food and water. When water was cut off, the result was very different from what occurs in a terminal patient. Not humane, and not "peaceful".
In simplest terms, the body's organs use water during the various life processes and 'pollute' it. The kidneys remove polluted water from the blood stream. The stomach and intestines replace the water the kidneys have removed with clean water.
If someone's kidneys have shut down, water will no longer be extracted from their bloodstream. Consequently, adding more water will not help the patient and may indeed be harmful. Unless the person receives dialysis, the blood will become more and more polluted until it can no longer sustain life, but this is hardly the worst way to die.
In someone like Terri, however, the kidneys will continue to extract water from the blood even though it is not being replaced. The amount of water in the blood will consequently drop to the point that the many of the person's capilaries become brittle and burst. Even though this is happening, though, the kidneys will keep on doing their job extracting polluted water from the blood. Although conditions will eventually get so bad that the kidneys quit functioning, the effects of dehydration on the rest of the body before that occurs are just plain nasty.
Your details do present some valid points.
However, I maintain that Terri Schiavo's body began shutting down fifteen years ago, and the feeding tube supplanted that natural shutdown. The dying process was therefore extended, and the organs had a chance to regenerate.
However, her brain did not, nor did the ability to chew and/or swallow.
Her parents took her home with her for three weeks (can't remember the year, it seems it was two years after her heart stopping, and before the malpractice suit award). They brought her back because they could NOT care for her. That was at least ten years ago. At that point, without ANY equivocation, Michael Schiavo was appointed guardian.