Why would you post such an idiotic article? It is non-sensical on its face. The article itself states the following:
The federal income tax in the U.S. (like most countries) taxes annual income, including realized gain on assets sold within the past year, but not unrealized gain on any increase in wealth. So, the discussion is idiotic.
It is just an argument for a wealth︀ tax using a self-serving and inaccurate analysis of U.S. income tax law. If your house︁ doubles in value over ten years, should you have to pay a wealth tax on︂ that increase in value even if you never sell it?