Is borrowing a clip to comment on it really the same as stealing the whole work? The other side leans on the idea that any use of someone else's footage is theft, but that flattens a real distinction. A reaction video adds commentary, context, and often criticism, which is exactly the kind of transformative use copyright law protects. And practically, plenty of original creators get new viewers from reactions. If someone just reuploads a full video with no input, sure, call that out. But that's not what the category is.