In most of my discussions with people living with dementia, they're expressing indignation, essentially, that they are not taken seriously with regard to their own wishes, because perhaps a future self is valued more than their current self.
Of course, there could be slippery-slope arguments, such that if somebody makes a request, it could be taken too far, or that somebody who's thought to be a trusted decision-maker perhaps makes a decision that is in their own self-interest as opposed to the person's interest, or perhaps they are constrained, despite what we hope, by economic or social circumstances. We know that a lot of people, particularly in their senior years, and especially those who have chronic medical conditions, have difficulties in terms of socio-economics and living situations and housing and whatnot. One can imagine, I suppose, different ways things could be taken too far in this slippery-slope type of argument.
However, maybe I'll bring it back. The other slippery slope is the uphill slope, when we don't allow people in their current state to exercise what they wish.