I would be more willing to accept it was a couple of bad eggs if the police hadn't started inventing laws about driving for exercise and fining people for crimes that don't exist.
The Guidance specifically says you can travel a short distance for exercise, e.g. to access an open space) and as pp demonstrates, the police are fining people for doing something they are expressly allowed to do.
This is lazy policing. There is a real law about face coverings, not to mention indoor mixing (which these officers were doing themselves), real laws that the police are reluctant to enforce.