"..says it’s hard to sympathize with consumers who are able to afford pricey coffee drinks but complain about tipping.." Hmm.. wat? I don't drink "pricey coffee drinks" (I'm cheap), but I think everyone can do whatever they want with their hard-earned money.

They should complain to their employer. If it doesn't work, to government as policy maker. As mentioned at the end of the article, "If you work for a company, it’s that company’s job to pay you for doing work for them"