Although this is horrible there is one thing that should be pointed out in the example used. The building was purchased for $2m in 1981 and it is worth $10m now. Why do they owe $7m on it? My guess is the owners lived large on the increasing value by borrowing on it.
Regardless of what they thought the tax laws would be, smarter would be to pay it off as soon as possible and live large on the income without the uncertainty of future tax law. They would still be getting ripped off but there would be something left over.
What's the death tax on a building bought for 40k in 1980 and worth now 5M?