This is a hot button, but I'll bite;-)
I do not think that you starve and dehydrate someone simply because they are disabled. Life matters and has value.
If, as I understand it, Terri was on no other life support except a feeding tube then she certainly deserved at least that much. Food and water is a simple thing. I also, to the best of my understanding, read that she might have been able to eat or drink on her own, but her husband wouldn't allow it for fear of her choking and....gasp....dying. Seems a little hypocrytical there if you ask me. Perhaps she didn't even need the feeding tube and she could have lived her life as a disabled woman until a natural death. Her parents would have happily taken care of her, but her husband wouldn't allow it.
The Terri Schaivo situation is an ethical can of worms on many levels, for sure. I also would admit that I only know what the media tells me, so that means I truly know nothing.
Would I want to be kept alive like that? I honestly don't know, but I would lean towards probably not. Would I allow someone else to live like that? All I can say is that I would never be the one to make that descision, to end a life that way.
You would be happy to know Candi, as another of your questions posed, that we do have Advanced Medical Directives. My mom recently had a stroke and was in ICU. We had a fantastic nurse who really advocated for us to have "that" conversation (pre brain surgury!) and gave us all paperwork to take home.
I am greatful that in my immediate family I won't have to make that descision. We have all made our own, and it is in writing. I would encourage everyone to have those conversations. It is not as difficult as you might think, and better now than later....like in and ICU ward.
I will add that I would have no moral issue pulling the plug, as it were, when I know for a fact that this is what my loved one wishes for their situation. I would always abide by anyones wishes, whether the same or different from my own.