I would argue that such a thing can not exist, since manipulation for gains is a rational approach to any market.

What kind of manipulation? I might exaggerate the quality of my shoes, or negotiate with the farmer to get an extra bushel of wheat, but we still make a voluntary exchange, each of us judging that we are improved by the trade, or we make no exchange at all.

a 'free market' requires altruism

Why so? I may despise the farmer, and yet crave his wheat. People do business every day with strangers, without caring particularly about their welfare.

the checks and balances intrinsic to a 'free market' can be overcome with collusion

Collusion isn't that reliable. There are substitutes available for the vast majority of privately provided goods and services, and providers must compete on price. Such monopolies as have appeared typically dominated the market by underpricing the competition or enlisting the aid of government to keep the competition down.

I'm not sure that there is evidence that it suppressed economic activity.

Such evidence would be difficult to come by. People would still work up to the point where they don't consider it worthwhile to work more. I find it plausible that a law which changes ownership of large amounts of wealth will affect people's behavior, and to the extent it changes behavior, it will be in the direction of avoiding the change (by taking more leisure, incorporating overseas, using tax dodges, and cheating). There may be subtle unseen effects, as well. A college student, seeing that there is no additional monetary benefit to pursuing a very-highly-paid profession, might decide instead to pursue a less-highly-paid field.

Since the government spends that money, it might be a wash.

It might be a wash, or you might get taken to the cleaners. No sensible people consider donations to the Treasury a realistic act of charity or investment. People spend their own money more carefully than they spend other people's money. And it's not automatically beneficial just because funds are spent -- government often spends money on things taxpayers find objectionable. In particular, government is frequently an enabler of "the centralization of power that comes with the concentration of capital."