I'd be tempted to agree with you if he didn't have another honey by whom he has fathered two kids and who he has called his fiancee. I still don't think he as guardian should have the right to carry out supposed oral right-to-die wishes with no written evidence, although he appears to under FL law, or Judge Greer's law.
They MAY be legally still married (at what point if any in FL does living together and having kids constitute common-law marriage?), but certainly aren't in substance. Because of the adultery, which began even as he was suing for money to treat Terri, they aren't one flesh any more than you and I are.
Morally, I completely agree with you. Unfortunately, as I have said in a previous post, what is moral is not necessarily legal, and what is legal is not necessarily moral.
I will also add, that based on the poligamy practiced in the old testament, this would be completely moral.
The key here is that once a female is married, under Christian precepts, she "belongs to" her husband as much as he belongs to her. And her parents are most definitely out of the decision making loop unless they can prove criminal behavior.
I have three adult daughters. Once they are "hitched" they are no longer mine. And love him or hate him, I will not presume to be able to "tell" their husband how to treat them. I may only offer advise which he has the right to accept or reject.