I suspect these are just code phrases for "If they can't vocally protest or physically resist, their lives aren't worth living anyway. Kill them, plug them in the ground, save some dough, collect the insurance, and open up a hospital bed. Next."
I don't understand some of your thinking. I believe we are in agreement against euthanasia, but I don't dump living wills into that same catagory.
Euthansia is the active taking of life. The vast majority living wills are not necessarly any thing about that. Living wills are about refusing some forms of medical treatment.
Terri Schaivo situation is really a horrible example to have for living wills and end of life discussion, because the medical and ethical decisions that had to be made in her regard are not what most end of life decisions are surrounding.