I think one of the big issues here is that many of us perceived Michael's behavior as being far more consistent with a man who is hiding something than with a loving husband. If, in fact, Terri would have been unable to swallow, Michael could likely have gotten rid of her in October 2003 by simply allowing the parents to try to give her food and water by mouth. Terri would probably have gotten nowhere near the support she got if people perceived that Michael was acting in good faith; without that support, the legislature would have never signed the 2003 Terri's Law, and Terri would have died about 18 months ago.
Why, then, has Michael so consistently refused to act in a manner that would defuse public criticism? The only answers I can figure that make any sense are:
Those seem to me to be the two most obvious motivations. If feeding her by mouth would choke her, well, he was trying to kill her anyway.