We're talking about a land value tax, not a property tax. They're quite different, and if you're curious about the logic behind them then by all means read the original article, or the Wikipedia article on Georgism, both of which go into some detail. Also, note that a land value tax would be progressive, not regressive.
Also, while obviously they could be wrong, if Krugman and Stiglitz think it's a good idea, and Marx was afraid it would help the proletariat out so much that it would delay the revolution, it's probably a sign that it's not as obviously "extraordinarily evil toward the bottom ~50%" as you seem to imagine.
I think it's likely that 'adventured' understands the difference, and chose Turner as the example because he owns 2,000,000 acres (~100000 hectares) of mostly unimproved ranch land: http://www.tedturner.com/turner-ranches/
This makes him the second largest landowner in North America, after John Malone.
Also, while obviously they could be wrong, if Krugman and Stiglitz think it's a good idea, and Marx was afraid it would help the proletariat out so much that it would delay the revolution, it's probably a sign that it's not as obviously "extraordinarily evil toward the bottom ~50%" as you seem to imagine.