Eamonn O Brien
I know from experience that there's nothing you can say to these people that will prevent them from detaining you if one is driving illegally and thus in their eyes, breaking the law...
I've gone over possible conversations with these people in my head hundreds of times in preparation :p
If there's no breach of the peace then I don't understand their intent. Let them know that. They have to do what they have to do and vice versa... Notice of mistake can do the talking after that :D