The most impactful way consumers can assert their power is to become mindful shoppers giving their dollars only to socially responsible companies. In today's world of social media and smart phones this is easy to do.
Credit or debit cards for starters are nothing short of shoppers' Novocain. Even in the age of digital purchases and virtual money we still attach a special value to dirty paper with pictures of presidents on it. Handing some of that to a cashier simply hurts more than handing over a little sliver of plastic.
Experience does not err. Only your judgments err by expecting from her what is not in her power.