The flaw at the root of Liberal thinking is the same thing that makes Liberals so arrogant. They know their ideas can work on paper, where you can leave out the human factor. The idea that every member of a society will produce to his best capacity while only using what he really needs is a fine one, as long as you leave it to insects or robots and not try to force flawed, imperfect, self-aware human beings to live by such a system. People will hoard goods, engage in black markets, slack off work whenever they can and bribe officials to avoid unpleasant duties. Liberals seem to think that people can be made perfect if the right laws are passed, and if you teach them young enough. But to make that system work in the real world, you have to enforce the laws with heavy police presence, cameras everywhere, indoctrination and secret police... and you end up living in the novel 1984. 

The idea that you can simply tax wealthy people and corporations to get money works fine... as long as those entities don't find a way to hide their money, avoid the tax using influence with politicians and officials, or pass the tax along to consumers. In the real world, that's exactly what happens -- plus it destroys the only valid incentive for hard work. But taxing wealth works on paper, so obviously it's a perfect idea. Again, the only way to make it function in the real world is total government control, which ends with everyone (except the ruling class) being equally destitute and miserable.

The problem starts with the way college students, especially, are taught to examine a problem: by taking it out of context, disconnecting it from outside influences and consequences. If you tax entity A you will always generate X amount of revenue, on paper. But in the real world, every action has consequences and repercussions, everything is connected to everything else, and human nature cannot simply be left out of the equation. Entity A will hide his money in tax shelters, charge Entity B more for his goods, fire Entity C to save paying his salary, bribe Entity D and make campaign donations to Entity E's re-election campaign to avoid paying that tax out of his own pocket.

Real life is far more complicated than Liberals seem to comprehend. That's why their solutions to the problems we face are usually both simplistic and unrealistic. But they work on paper, so we're the stupid ones.