You want to allow the website YouTube.com but filter some of the videos on the website.
Due to the way YouTube.com is built, K9 cannot currently separate the difference between videos. It only knows that each video is being accessed through YouTube.com. As such, only the entire YouTube site can be blocked or allowed at this time. Videos cannot be filtered individually. We hope to revisit this ability in the future, but it may not be possible until YouTube changes how their site is built.
We recommend that if you are concerned about content on YouTube, that you leave the web site blocked and when users would like to view YouTube videos you allow the web site temporarily, when you can supervise their viewing.