Accepting what you say as the basic theological orientation of those who object to AL, their position is still easily countered from within their own frame of reference. They do indeed argue that "....anyone who approaches the sacrament in the state of sin does so unworthily (borrowing a Pauline phrase) and commits a sin." And they go on to assert that a remarried divorcee is objectively living in a state of mortal sin. What they do not acknowledge is that, based on their own orthodox reasoning, such a state only applies under 3 conditions: 1) grave or serious matter (tick); 2) full knowledge of what they are doing (maybe tick); and 3) full consent of the will. The whole point of the AL footnote is to address those whose lives are in a murky mess: extricating themselves from their relationship and/or living a brother-sister relationship is very complicated if not infeasible. There is no full consent of the will. By traditional standards of reasoning, communion is valid in such cases.