A.S., I appreciate that you're just venting, but I suppose this is a good example of a situation which the investigator should avoid entirely.
Although by your actions you are seeking to protect your client's interests, it nevertheless prejudices your client's privilege to make his own decision on how to handle this matter. It could, potentially, get out of hand.
I had always made it a rule never to "enter into correspondence" with a solicitor for the subject of investigation except to confirm instructions from my client to investigate or to make an appointment for an interview with his client.
Food for thought
BigGeorge