Full disclosure....I am a middle aged white male moderate liberal.
OK, if the employees are telling the truth (and that is a big IF), I can somewhat see their side. They are valued employees because they are bilingual and can communicate with the Spanish speaking only customers. A very common issue in retail. And presumably, Spanish is their first language and thus their language of choice. I can understand them not liking a policy of not being allow to speak their first language to other employees.
However, Whole Foods tells a different story....and I tend to believe them.