How do I get my parents to acknowledge that they have Alzheimer's?

Both of my parents have been diagnosed with early Alzheimer's. (My Mom has had memory problems longer than my Dad.) But they both behave as if nothing's wrong with them. My brother moved them to an assisted living facility this summer. Since they aren't aware of their conditions (either their own or each other's), they don't understand why they need to be there. While they're adjusting to the facility, they think it's temporary and hope to return to their home in time for the holidays.

Their relatives and friends are all in agreement with my brother and me that they need to be in an assisted living facility. My Dad's driving has been a big concern. (My Mom hasn't driven for a few years now.) They've lived in the same city for over 40 years. It's an average-size city, and they were able to get around quite well until the past few years. Then they started getting lost when they went to places they didn’t go to very often. Sometimes, my Dad dropped my Mom of at a hairdresser or doctors’ office, and then forgot where he left her. Last year, they made an 100-mile out-of-town trip to relatives that they've made 100s of times, and that should have taken only 2-3 hours. The trip ended up taking them almost 12 hours!

They also neglected to pay bills, and let them pile up for months at a time. At one point, they almost defaulted on their mortgage. One year, they didn’t pay their taxes on time.

But it's impossible to have a discussion with them about these problems. They get very defensive when anyone tries to talk about their conditions with them. I'm assuming their short-term memories has deteriorated to the point they don't remember these memory lapses after a day or to. (Besides forgetting the memory lapses, another example of short-term memory loss is they've forgotten about recent visits from friends or phone calls after a few days.)

Any advice on how to discuss my parents' conditions with them would be greatly appreciated.