Showing that you're willing to pay extra for green products (or products that respect animal welfare, etc) creates a competitive environment in which companies

Showing that you're willing to pay extra for green products (or products that respect animal welfare, etc) creates a competitive environment in which companies can compete on who provides the most green per dollar. Even if those marked up products are all just greenwashed today, it still creates a market opportunity for new companies to come in and outcompete today's greenwashers with products that deliver better green per dollar in the future.