I don't flag. Yesterday I found a direct copy of a YT video, but rather than flag I confronted the poster with the original he had copied and uploaded to DTube. I pointed out to him that he is denying the original creator the views, likes and comments as the same happened to me when people uploaded my work on their FB accounts. Those views ultimately weigh in on whether your channel grows or not and you can't get the views back under DMCA. He corrected the post by linking to the original YT video. Problem solved.