The video is found here: Answers to 12 Bad Anti-Free Speech Arguments. There was a time when those on the left liked to argue but that was a long time ago. The left believe they no longer have to listen to anyone, and therefore no longer do. The result is the growing catastrophe we see before us.
For more detail on Mill and free speech go here: Mill’s Argument for Free Speech: A Guide. There you will come across this actual quote from Mill:
…the peculiar evil of silencing the expression of an opinion is that it is robbing the human race; posterity as well as the existing generation; those who dissent from the opinion, still more than those who hold it. If the opinion is right, they are deprived of the opportunity of exchanging error for truth; if wrong, they lose, what is almost as great a benefit, the clearer perception and livelier impression of truth produced by its collision with error.
Shutting someone up is not free speech.