I'll start by saying I'm no lawyer so what I'm about to say could be well off the mark.
I think if the email we (EDITED TO ADD: We as in the legit Paintball community. Lead in this case by Pete) got from plod was gen (which it seems to be) then it's a case of a crime has been reported by our hero (harassment or whatever he perceives the crime to be) and the woman in blue sent a fairly generic email to stop that. I doubt the thread was read in its entirety and the email sent was in hopes that the posts would be deleted and Jamie would shut up and go away. Easy closed case and everyone is a winner. I'm led to believe that the police should remain neutral, gather evidence, and act according to evidence such as making arrests or referring to court.
As said, I could be wrong, but the above is my guess
Effectively as you have said except a crime was not alledged, probably just a complaint - either along the lines of:
'my personal information has been put on the internet and I want it taken down' or
'I am a child and my personal information has been put on the internet and I want it taken down' or
'my / our childs personal information has been put on the internet and I/we want it taken down'
Circumstances of some form were acknowledged and the police officer asked Robbo to act and remove the information
Robbo responded supporting the forum policy, considering the information is appropriate, gave his reasons, stated it will not be removed.
Simple as that. The officer will come back to Robbo having seen the rest of the information and things will go from there. They may pursue the complaint, they may close the complaint, they may deal with the original issue.