Re talking to the police in the first instance: I'm a bit surprised Mr. Miller never informed the police that he did not wish to discuss the matter with them - the police asked him to appear for a 'voluntary chat'.
The usual tactic by the police if someone refuses the voluntary chat (which people can legally do) is for the police then to go through the person of interest's affairs and try to pin anything illegal on that person. If they find nothing illegal, they'll watch that person until he breaks the law.
It's disgusting behaviour from the police - they should be solving actual crimes.
'Checking people's thinking' goes beyond their remit. People are free to think whatever the hell they like.