Seems to me this is about a lot of things...but the wishes and best interests of Teri Schiavo ain't one of them.
Actually, there have been several cases like that. Parents who are Christian Scientists do not have the legal right to refuse medical treatment for their sick child, and Christian Scientist (CS) parents have been prosecuted for child endangerment and even manslaughter. I believe the legal standard right now is that CSs have no right to refuse medical treatment for their children, although any CS over the age of 18 can refuse on their own behalf. I do not know whether this can be classified as a "left vs. right" issue.