Fair use of copyrighted material is an extremely complex situation and is often dependent on how a particular court will view it as. It is more than just giving credit to someone else for their own copyrighted material, it is that the material cannot be distributed without the permission of the copyright owner. If you rebroadcast an NFL game, no one is thinking that you have created the content but that doesn't mean that you're not violating copyright material.
Generally, to not infringe on someone else's copyright you cannot use large amounts of the original material or you have to change it in some significant way. Some examples you can see on the internet is the videos Everything Wrong With..., where they will show clips of a movie and then mock it. They generally don't play the audio along with the video, this does two things it allows them to mock the movie but it also allows them to change the original content to help them get by copyright laws. That doesn't always work and many movie studios have gotten YouTube to take down their copyrighted material. They also will take a 90-minute movie and only show a fraction of the content down to like 15 minutes or less, again not showing the whole content but only a relatively small portion.
If you want to say a letter came out and it discusses xyz and then speaks about it that is certainly freedom of speech, but you cannot read the whole letter out and then say, well I interjected criticism, therefore, it is fair use. You could do that to any copyrighted work and then there would be no protection for anyone.
Same thing goes to playing an entire convention recording and saying because I stop it regularly to interject my comments, therefore, it is fair use under the criticism doctrine may or may not hold water. You have to be prepared to defend your reasons behind it.
And then there are some Ex-JW activists that don't just do it with Watchtower copyrighted material but also to the commercial copyrighted material. Six Screens uses music that is copyrighted by artists and even by NBC. So it may not just be watchtower that sends these out against EX JWs but it could be commercial ventures that own copyrighted material otherwise.
Again copyright law is extremely complex that is why there aren't a lot of IP attorney's out there, and the ones that are out there will tell you that it is rarely ever cut and dry.
As a side note, Cedars has been going on with his twitter account about how he isn't getting paid for some of his videos. When people do stuff like that, they become even more susceptible to copyright violation notices because it is proof that you are making money off of it and not just doing it for nonmonetary reasons.