how can I accept that if a loved one with dementia is an ass it's not really his fault, but the illness?

Dementia runs in my family, and I've, unfortunately, had a lot of experience with nearly every type of dementia patient in family members I've helped care for. The solutions, in order of how optimal they've been for each afflicted family member, have been:

1. In-home healthcare
2. Group home
3. Nursing home/care facility

The thing that makes in-home healthcare so optimal is that your family member has a less difficult transition and receives the highest individual care. But it can still be a nightmare for you and it can be incredibly expensive.

Group homes are often a bit more of a black box, since getting certified as a group home is easier to game than it should be. But you still get that highly individual care, and someone is almost always around to help out with a fall.

Nursing homes and care facilities are the same as a company in that the quality is only as good as every cog in the machine. We've had some incredible experiences at nursing homes, but it's all too often that the one nurse, the one with an incredible attitude who's been there for years, leaves, and suddenly the morale and quality of care globally plummets.

No matter what you choose, there's one important thing to remember: because this family member can't take care of themself anymore, they're relying on you for their own care and happiness—you can't provide care and happiness when you're drowning in misery. If you can afford some form of professional care for this person, that will be the best solution for you, and ultimately provide the best solution for this person who you obviously care enough about to have this level of concern.

If professional healthcare is financially out of reach, contract some of the nursing homes and local community centers to ask them for information about programs and services. Let them know that you're doing this on your own and can't afford professional care. They'll almost always be more than happy to tell you about free or cheap services and programs that will greatly lessen your load.