If you post content on YouTube that includes third party copyright works, and the owner of such third party copyright works lodges a take down notice with YouTube, YouTube will not assess whether you have any valid defences, such as fair dealing. They will – if the fair dealing is readily apparent – sometimes specifically ask the person lodging the take down notice to confirm that they have considered this defence. But if the person claims that they have considered it, YouTube will not make the determination of fair dealing itself, and will proceed to remove the content and issue a strike against the person posting it.
If a person receives 3 strikes in a 90 day period, the person will have their YouTube channel permanently removed.
Thus, including third party copyright works in any content posted to YouTube – even where those third party copyright works are legitimately included by way of fair dealing – poses significant risk to the holder of a YouTube channel.