Your free speech is not infringed just because someone decides to close down the comment section on his youtube chanel. I have no clue, why anyone would get that idea, because no one is forced to seek a conversation or accept comments from someone on a video they released. All you're doing on youtube, is to share something. What ever if people want to watch it or not, is up to them. This is the beauty of it. If you feel you have to say something about a video, then you can make your own and upload it to youtube and that's it. But you can not, nor should you force people to listen to what you have to say. Hypothetically speaking, if I wouldn't want to read what you write here, then I can simply add you to my ignore list for example. How's that a viollation of your free speech?