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YouTube Video Recommendations Lead to More Extremist Content for Right-Leaning Users, Researchers Suggest
(lettersandscience.ucdavis.edu)
This is a most excellent place for technology news and articles.
Thumbs down actually makes Youtube recommend more stuff to you because you've engaged with the content. As said by other people, best way to avoid recommendations you don't want is to just ignore the content and not watch it, if it's being recommended to you then click the three dots on the video thumbnail and choose "not interested"/"don't recommend channel".