It's a flag created by YouTube specifically for Hasbara. It's for flagging anti-Israel videos, not anti-semitic videos. Although the people working for Hasbara would like you to think they're the same thing.
https://www.youtube.com/watch?v=Vqhi16iikxk
https://www.reddit.com/r/conspiracy/comments/6xjxj7/shut_it_down/
Finally got CliWrap, my command line interface wrapper library, feature complete. Meanwhile YouTube removed some AJAX endpoints that broke YoutubeExplode.
Your best bet is to just find the ffmpeg process and kill it off manually. Or you can use managed tools such as YoutubeExplode and YoutubeExplode.Converter
You have a project reference to YoutubeExtractor, but it's not part of the repository.
Also, you might consider using YoutubeExplode instead, because YoutubeExtractor is not maintained anymore, as seen by the issues.
As it's kinda funny, I wanted to add that YoutubeExplode (which is the library YoutubeDownloader is based on) was the first to implement a throttling-bypass workaround for downloading adaptive streams (30-Jan-2018 vs 04-Feb-2018). As it is now, YoutubeExplode is also the only library (to my knowledge) that completely foregoes signature deciphering for protected videos, which cuts the stream download time significantly.
Not directly an answer to your question, but just pointing out that YoutubeDownloader may also have some advantages on the technical side of things too.
Try cloning the project and editing this file. Make sure you open the actual project so that IntelliSense works, because I suspect it's the main culprit. There's a static dictionary towards the bottom, when I copy and paste an item to make a new one, and then edit one of the passed enum values, the VS just freezes. I actually use a separate text editor to edit this file now, lol.