INTERESTING, BUT NOT RELEVANT. Terri Schiavo is not in the last stages of terminal illness. She's not even ill - let alone have a terminal disease. But she IS one of thousands of people around the country who have severe brain damage. ARE WE GOING TO KILL THEM ALL? I don't see any logic that allows us to kill Terri but to spare the thousands of others who are in similar physical state - whether it's PVS or minimal consciousness, or whatever it's diagnosed.
THAT'S WHAT THIS CASE IS ABOUT -- whether we start down the path of killing severely disabled people because we've made a determination that they would be better off dead.
You point out that feed tubes are pulled with some regularity from terminally ill elderly people. Whether that's right or wrong - and it depends on the particular circumstances of each case - it simply is not relevant to the question of whether we should start withholding nourishment from brain damaged people who otherwise ARE NOT DYING. That would be a HUGE change in policy in the US. And yes, it would start us down the German road - because this is what Germany did in the 30s - it made a decision that the severely disabled were better off dead. That decision had consequences that didn't stop with the severely disabled.
I remember reading once that the concentration camp guards who balked at killing Jewish children were told that it was a humane thing to do, since having to live while being Jewish is a horrible fate, far worse than death.