Wasn't the communication from the producer of the KNOCKING film, or someone similar? Is it at all possible for V to respond to the message by explaining that the brief clip was used with the good-faith assumption that such use was permissible as "fair use" (considering the brief length, use in illustrating the purpose of the video as commentary, and non-commercial use), and if it has turned out not to be the case, could he still make a request for permission to use the clip (with an acknowledgement indicated on the page for each video)? I understand that granting permission may be unlikely, but when is it too late to ask?
I honestly think this is your best bet. If you want to not go through the trouble of having ro re record everything, just try this approach, and see if it works. It may not work, but it may...