It is the Daily Mail, of course it is a joke.
Why you people buy the rag when it sends your blood boiling, I don't know. Perhaps you enjoy being outraged.
That is a particularly brilliant example.
The police service (not force you will notice) have to deal with the public in all its many facets. This is an example of training. If you work in a shop or a bar part of your training will be serve someone, another member of staff will act the role of a customer. That is all that is happening with this training exercise. The police are putting themselves in the shoes of the community it is serving.
Police use role playing in training all the time. They even pretend to be criminals sometimes, one was tragically shot last year. At the time no one said he was wasting time or should have been out catching real criminals, but then, he wasn't dressed as an ethnic.
http://www.dailymail.co.uk/news/article-102523 4/First-picture-police-officer-shot-dead-role- play-exercise.html