What was false? Yes, you can obviously form an opinion about something immediately after you've watched it. That's not what was stated. I said you that cannot criticize UNDER FAIR USE in this manner. Streaming a copy of the content to your viewers through a "watch party", and criticizing it, is not covered by fair use. This is exactly the same as renting a movie, streaming it, and then making some comments.
Fair Use effectively allows you to reference the original work to illustrate or show the subject of your critique (or any other covered use). You're not referencing anything if you haven't seen it before. The Fair Use doctrine does not cover playing copyrighted work that you simply intend to criticize.