The argument doesn't really make assumptions about how you contribute to a business. Investors fighting for higher capital gains also drive up the costs for the business they fund.

Higher ROI is how an investor increases her wealth relative to other members of society. Lower capital gains make the society richer overall.

If you invest your savings in a space business and genuinely care about it, then the return you demand becomes the cost of space exploration. Identical dilemma to that of the worker.

The class warfare between owners of capital and workers is essentially the same mechanics but taken between two specially chosen groups. In general, each individual and each group seeks to increase their share relative to others (whether you call it income or capital gains). Costs going down is how we all get richer as a society (the costs including both paychecks and capital gains).