It is a documentary. Which has been on YouTube for over a year. Which has very strict and clear guidelines.
YouTube would have removed it long before now if it breached any guidelines ~ including any terrorism guidelines. They are extremely on the ball when it comes to that. Also, no doubt that the video would have been reported many times by certain individuals so it will have been reviewed plenty times as it is.
Someone being in a documentary is not "promoting terrorism"
It is a serious allegation that you are making against YouTube.