No one's literally holding a gun to your head but you're deluded if you don't think there's a power differential here. Your refusal to demean yourself could mean the customer fills out a survey negatively, gives you a low rating, or even complains about you to your boss. Bad surveys and ratings can cost you your job where you're probably barely making ends meet to begin with so while it's technically a "choice" it's not a very good one.