I'm usually very much on the side of the small(er) YouTubers who have to deal with these bullshit, broadstroke copyright claims by large media companies, but then I looked at the original HellBoy trailer reaction video. It contained the entire trailer, in full, no editing. I can't imagine any court deeming this is fair use. You couldn't just take a video of an entire movie, add some commentary to it, and expect a fair use defense to stand.