Securities are valuable assets for the same reason that greenbacks have value: because the state is standing there ensuring everyone's playing a fair game. If the state didn't punish counterfeiting, greenbacks would be worthless. If the state didn't punish non-dilutive duplicate share sales (i.e. selling the same whole pie to two people), securities would be worthless.
As such, the state is creating the worth of those things, from nothing. Your effort into a corporation is additive, but the government's pre-invested effort into building the framework on which corporations rest is multiplicative, with the multiplier having started off, before that effort, at 0. Neither fiat money nor securities work in a lawless world. The government—that is, the People—get all the credit for making those things possible. Should they thus not get the reward? (Commodities do work in a lawless world, but not through tokens representing them. You'd have to bring those 10K bushels of wheat along with you if you want any credibility, which is pretty inefficient.)
Let me put it this way: if we were starting with a form of socialism where corporations exist, and have founders and executives and boards of directors, but no shareholders, with the government instead earning all corporate profits (which it then spends on things like UBI); and then someone proposed a capitalist class that would earn some of those profits instead, taking them directly out of the UBI budget... would that proposal be justifiable through any particular argument to natural rights/freedoms? There might be a practical argument, in terms of a profit motive incentivizing entrepreneurship and investment, leading to a "rising tide"; but would there be an ethical argument in favor?
> History has not been kind to nations whose governments break those rules and started nationalizing corporations. Not too long ago, North Korea was the side with the industry, railroads, hydro-elec dams, steel mills and manufacturing plants.
North Korea isn't a particularly good example; their economic stall is a result of trade embargoes more than anything. (They're actually doing as well as could be expected, given that they're an isolated, non-globalized economy whose only trading partners are much larger globalized economies [China, Russia] who don't need anything NK could provide.)
Meanwhile, China's own mostly-nationalized corporations do pretty well for themselves.
Hell, even Canada has tons of Crown Corporations, and everyone here is begging our federal government to nationalize the cellular infrastructure (and then lease it out fairly) because it'd be much better than the current oligopoly situation we're in.