Anyone in customer service should be friendly to customers or they should find another type of job. It's rude and makes me not want to go back to a place where the service was rude.
I don't think they should be replaced with robots though because, there are people who are friendly with customers so they might lose their job too. I do though think when someone is rude to a customer, they should be fired or at least be written up. There are too many other people who are looking for work who would be glad to treat customers with respect and get paid for it.