That you did not perform significant work for it, and did not take a significant risk.
By taxing those earnings you reduce the demand for the shares which then reduces the amount of money the original workers can raise by selling shares.
The secondary market provides incentive to invest in companies.
Why is it that people of certain political persuasions always seem incapable of thinking through second and third order effects?
I am certain spending could be better allocated, but should corporations and billionaires be getting a free ride when they are gaining so so much from society? What are the downsides to taxing them more?
Billionaires and corporations are a misdirection, the actual policy that they will push is to raise taxes on people making upper middle class salaries.
And that is for me - there are people who inherit fortunes, who by virtue of having fortunes, and who invest in anything sensible, even an index, will never need to work and contribute, and are virtual kings. This is a hard kink to iron out in capitalism.
In addition those who have fortunes and decide to work hard may direct that work into getting more unfair advantages (lobbying, for example, to ban better mousetraps) rather than doing stuff for the greater good (making better mousetraps). I think this too is a problem.
Capitalism + government intervention + free speech/debate might be as good as it can be for now, until abundance.
Capitalism is the worst economic system, except for all the others.
Sometimes this is physical, like manufacturing machines that can be used to produce material goods that people want. Sometimes it is virtual, like the monopoly on force that forces people to pay taxes.
What if these things are offloaded to a secondary party, in exchange for a portion of the returns?