If all other corporations raise wages and get the economy going (assuming for the moment that he's correct about this mechanism) I can keep the wages of my company down and still enjoy the benefits. And I can't make the economy stimulated just by raising the wages of my company's employees.
It would take some form of collective bargaining for this to work
Yes precisely - this would have to be mandated by the State, and you point out very well why 'private' industry is so disastrous for the economy as a whole (unless it is only 'private' in a legalistic pretense but in practice closely managed by the State).
Most sensible people (or just anyone who's taken a sufficient amount of economics) know that private actors can't optimize everything. A lot of things are better left to private actors though, for various reasons that I suspect you would recognize if you wanted to.
