Hold on a minute -
As immigrants, many of us have been in situations where we felt frustrated and confused because we didn't understand a British phrase or custom, or a British person didn't understand us - and we all have the advantage of having some form of English as a native language.
When a police officer has a conversation with someone, there is a good chance that his is having that conversation in response to a difficult situation - and speaking with someone who is very angry, frightened or confused; may be in pain, behaving violently, etc.
In such a situation, why make things worse by using language that could be confusing or could offend someone? Which is more important, trying to calm down an agitated person or using a non-PC word in order to defend your right to free speech?
If anyone should be be careful of the language that they use, it's a police officer.