What real world value to long buyers add? Sure, if you invest and the company takes that investment and does really well with it, the world may benefit from an increase in productivity/wealth. But if you invest and the company does poorly and tanks, then the world loses by something because you could have taken that money somewhere productive. The kind of market that produces the most real world value is one where companies are valued accurately. If you think a stock is undervalued, you go long. If you think it's overvalued, you go short. Both actions affect the market value of a stock.
Seems like two sides of the same coin. I can't see where an argument against one doesn't work against the other.
Now, the stock is the product, not the company. It's become a game in itself. It adds nothing to the real world outside of finance.