That appears to be with regard to employment discrimination. I wouldn't be surprised if there were slightly different standards for serving customers, etc.
I don't think there is any prohibition on age discrimination for public accommodations. Title II of the Civil Rights Act forbids discrimination on the basis of race, color, religion or national origin and Title II of the Americans with Disabilities Act covers discrimination on the basis of disabilities, but there doesn't seem to be anything preventing public accommodations from discriminating based on age. The Age Discrimination in Employment Act, which is what prohibits employers from discriminating based on age, doesn't contain anything about public accommodations.