Earlier quoted context omitted.
Paying taxes on unearned gains is not "driven out of your house". You can keep the house and pay taxes on the gains. > I’m sure your feelings will change as you get older. Yes, this is the problem. Extreme self-interest and entitlement to massive windfalls.
How are old people with no income supposed to afford capital gains taxes? And if house prices go down do they get a refund?
There is very little controversy over not taxing unrealized gains when it comes to income tax [1]. I'm not sure why doing the same thing for unrealized gains in property value is controversial.
It's not like most of the things property taxes pay for are proportional to the value of the property. The changes each year in costs to provide roads, schools, libraries, police and fire, and utilities to my house and my neighbor's houses generally has little to do with the changes in the market value of our homes. So why should the taxes that pay those things be tied to market value of the house?
More sensible would be to take the costs to provide the services the tax pays for, and divide it among the houses that receive the services, equally or taking into account usage (e.g., the amount for sewer might be proportional to the number of bedrooms). If we want it to be a progressive tax, apportion it according to the relative market values of the properties, but determine the total amount for the neighborhood solely by how much money the tax needs to raise to provide the services used by that neighborhood.
[1] There is controversy over tricks and schemes used to effectively realize them while escaping taxation.