I'm sure Band on the Run could shed some light on the legal issues, but I think it unlikely that the WTBS would so. First, it can't be libel if you're using their own material. It could be a copyright violation, but if youtube is taking down the videos when notified of the violation, the issue has been addressed.
If they did sue, the real fun would start in discovery. The defendants can ask all the questions they want, and ask for all the materials they want. They could, for example, ask for a copy of every article or talk outline containing "1975." The production would be costly and the results create more problems than the suit would solve. From a PR standpoint, there best bet is to lay low.