Well, lets go ahead and rip the article apart.  We'll call it constructive criticism to help the author better identify the evils to be railed against as opposed to the collateral damage the author inflicts on innocent concepts.  We may be able to get a better article that is more soundly grounded in logic.

First, we come to the story of the wealthy landowner.  In this contrived, idealized world, one person has a monopoly on land; one person has a monopoloy on all wealth.  The world is finite with no opportunity to migrate away or go fishing.  One cannot pick up a guitar and become a minstrel; one cannot write stories to entertain ones friends.  People cannot invent, nor can they teach.  Certainly the explotation of the monopoly is evil, but to blame this on investment income is wrong.  And this world is so idealized that we must be careful applying its lessons to our own world.

We next come to an example of a person who owns two houses and rents one of them out.  Let's modify this story somewhat and assume the owner built one or both of the houses.  In this case, the house contains the value of the labor that the person spent constructing the house.  The tools and materials the person bought to build the house similarily represent the individual's labor, saved over some period of time.  So a person who has bought a house has spent saved labor in order to obtain that house.  It is reasonable and fair for the person to receive payment for their stored labor.

In this case, the builder also planned ahead and made predictions about an inherently uncertain future.  The builder gave up the luxuries his labor entitled him to in his youth planning on getting repaid for that labor in his (or her) old age.  The indvidual is entitled to additional payments based on the risk he undertook when predicting the future, the stress that he underwent while worry about whether or not he would find people who could afford to pay him what the house is worth.

In the next example, speculative investments…  The paragraph is facile.  When buying the stock of a company, one is spending stored labor to buy a piece of the company.  The buyer is giving the company stored labor that the company can spend to produce new value.  The buyer is certainly entitled to the value of that stored labor.  The buyer could have used that stored labor to produce an income stream for themself.  He might have bought a fishing pole and used it to catch fish that he could eat each day.  Companies, however, by using specialised skills from a varitey of people instead of the skills of a single indvidual can frequently produce more new value from that stored labor than the buyer of the company could produce.  The person who stores labor for the future is entitled to a share of the value that the stored labor helps to produce.

It's not freeloading.  It's getting paid for work done at an earlier time.

Continuing through the article, I've previously explained why Money is not a zero-sum system.

The idea that invested money cannot create value is just silly.  You can't pick and choose when you decide that money is a representation of value.  Money is *always* a representation of value.  Created value can be used to create new value.  When a person creates a plow, that plow can be used to increase the amount of land farmed, creating additional value.  When one builds an irrigaton system, the value of the irrigation can be used to grow more food than before, creating additonal value.  Invested money represents the buying of existing value which is then used to produce new value which is then translated back into money.

When I receive investment income, I am not being paid for someone else's work.  The investment represents value that I'm handing to the worker.  Maybe I'm giving them a new tractor.  The return on investment represents some fraction of the value stream that the tractor helps the worker to create.  The worker gets a lot more than the value of their time without the tractor, the investor gets a fraction of the additional value stream.

Since three of the four propostions are flawed, one cannot conclude that investment income is unjust.

There is nothing wrong with getting paid multiple times for one's work.  Suppose I chip a piece of flint to make an spear head, and tie it to a stick.  So far I've invested quite a bit of work, and I've been paid, so far, with something that might as well be a piece of abstract art.  But now I use this spear, over and over and over, to produce more food than I could have gotten without the spear.  I'm getting paid over and over again for one piece of work.  And, my getting paid multiple times doesn't mean that someone else will get paid less.  I can give the spear to someone else, and they can get paid more than the would have gotten while giving me a small amount of the extra food they get from using the spear.

Moving down to "Compounding the Problem"…  Unearned income does not inevitably funnel wealth to the rich.  The example given is of a finite world.  Surprisingly, the author acknowledges this in the body of the text.  So to be accurate, investment income (since we've shown that it can be earned) funnels wealth to the rich in a closed environment.  We don't live in a closed environment.  So this section has no lessons for us, and we can ignore it.

The next section on Ruthless Corporations suggests that the world is finite.  Yes, it is finite, but in the same sense that the universe is finite.  It's going to take a serious amount of growth to approach that finiteness.  Sure, there's a finite number of interesting books that one can write using the english alphabet in 400 pages.  But even with exponential growth, it's going to take a damn long time to get all the books written.  Superconducting superconductors take a small amount of material arranged in innovative ways to create a lot of new value.  So does solar photovoltaics.  So does carbon fiber.

The paragraph does allude to the problem of corporations that make money by externalizing costs to society at large, but this evil is not investment income.  Some corporations may be ruthless and not have societies best interests at heart.  But that is a problem that should be addressed directly, not by saying that it is caused by investment income.  Corporations can do valuable, interesting things.  It is a good tool when used by the powers of light.  We must find ways to prevent the tool from being used for evil.

The section on Investment Income causing inflation contains a variety of assumptions and assertions.  But the underlying argument is not well motivated and well tied together with strict logic.  Baed on the chart, oh my god:  things must be really bad here in 2005 vs even 1930.  But how is it that we are living significantly longer on average?  How is it that obesity is one of the fastest growing medical problems in the U.S?  How does my family own three cars when my parents had two?  How do we have more university educated people  in 2005 than we did in 1930?  Sure, the number of dollars has grown by quite a bit, but the amount of value has also grown.  Yes, the dollars have been growing a lot faster than the value, but value has been growing exponentially.

And the final statement is bogus.  Inflation does not hit "someone else" twice.  Again, money represents value.  When we hand money to someone as an investment, it is converted at that days dollar-per-value exchange rates into underlying value.  The value is used to create new value.  The new value is converted back into dollars at the inflated exchange rate.  "Someone else" takes their cut of that new value and hands the investor a cut of that new value as well.

The "Hopeless Debt" section misses an important point.  If we can increase the rate at which we create value, we can overtake debt.  Public policy should not just be about cutting spending and raising taxes; it should also be about investing as a society to get more investment income for our society.  For example, college graduates make a lot more money than high school graduates.  Investing in our human capital by doubling the percentage of the population that graduates from a 4-year college would have a significant effect on the value available to our society.

The "Hopeless Debt" section certainly has a dramatic graph.  However both inflation and population growth contribute to the drama of the graph.  Wikipedia has a more intellectually honest graph at:  http://en.wikipedia.org/wiki/File:Federal_debt_to_GDP_-_2000_to_2010.png .