The helicopter said they had traffic (the airliner) in sight. Once you declare you have traffic in sight, it is up to you to maintain visual separation. The controller could tell them to turn (as they had them on radar and was receiving collision alerts). I can easily see the helicopter getting confused with which traffic they thought they had in sight (as an aircraft was taking off), and all the ground lighting doesn’t help. I don’t fault the crew, as I have been in many situations like this-nighttime, background lighting, confused and overwhelmed controller. Once they were off their altitude, the controller should step in and confirm the altitude, sometimes this is a wake-up call and gets you back into your proper scan. Sad none the less.
So air traffic control has that authority, good to know.