I guess I thought my 'vague statistics' were obvious and undeniable. If not, let's get concrete. Consider Union Carbide. They were responsible for the worst industrial disaster in history, with around 20,000 dead. They then went on to neither compensate the victims (including 40,000 permanent disabled) nor clean up the site.
This was widely publicized. According to your theory, such an extreme 'bad' act would have led to disaster for the company. In reality, it didn't even lead to rebranding. They were bought by Dow Chemicals - but that was because they had massive debts. I think they cannot have been related to the Bhopal disaster, since their compensation paid was very small.
One salient fact here is that moral hazard is not contagious. Many products are for other businesses, who aren't likely to pay a premium for ethical considerations. Another fact here is that even in the most famous and awful cases of bad companies, you're relying on the company's own branding to tell informed customers to stay away. Which is obviously extremely fragile - the company can rebrand, even if the customers are reliably informed (how many people on the street know about Bhopal? Is it present when they buy shrink wrap? Is it even possible to know that your shrink wrap was made using ethylene from union carbide?
All seems a bit absurd to me. Even before you get into the inherent asymetries of the idea (is Bill Gate's ethical opinion worth more than a billion poor people? As an ethical consumer, it is.)