McDonald's cashier's teaching manners to customers?

It is NOT their job to belittle the customers who pay their wages. There can be a lot of reasons why I might inadvertantly forget to say please - scanning a McDonalds menu for something nutritious could be one - and if I was pulled up about it by any service staff I would calmly walk out. I am a publican and I would be furious if my staff adopted this approach unless of course, the customer was being offensively rude or discourteous in which case I would support my staff to the hilt.