...what RAZD said. And...
Ms. Schiavo's desires are by no means invalid. But as we cannot objectively determine them, as we could if she left a will, we must speculate.
But you make them invalid when you ignore the best authority on what those wishes were, ie. her husband. Learned legal authorities have examined this and made an informed decision. End of story.
But shall we speculate? Maybe ask yourself, would YOU like the idea of being kept alive to spend the rest of your days in a hospital bed as a vegetable fed through a tube, nothing more than a mass of random bodily functions with your higher brain competely gone and no chance of recovery? Well, I wouldn't, and I find it difficult to imagine that any reasonable person would.