If a company policy is not illegal, then it is the company's right to dictate whatever policy they wish. If you don't agree, quit. As with so much of our current society, the tail wags the dog. I'm fed up with employee 'rights'. The employee is supposed to do the employer's bidding, not the other way around.
Definitely don't disagree...that said...if I could attract more customers by having Spanish speaking employees, I would want the language in my office...I would not want my employees to make English speaking customers feel uncomfortable.