Michael was enjoying the comfort of other women even before he began his euthenasia campaign. One woman was even with the blessing of Terri's parents.
My point is that one doesn't need to actively injure someone to contribute to their deterioration.
One can simply deny basic treatment and stimulation so that neglect and isolation can do the work.
You are correct that neglect can cause the brain to deteriorate ... it's been proven in newborns, sadly. My point is that such neglect wouldn't 'eliminate the albatross quickly enough'.