OTOH, if someone posts a video presumably it's for the purposes of discussion, isn't it? And it's hard to imagine a very interesting discussion where everyone completely agrees. So I'm not sure where the balance is, or what the ideal video discussion would look like.
Knee-jerk condemnation, automatic disparagement of what's different merely because it's different, soapboxing...none of these are discussion. None of these have anything to do with discussion. Discussion of a video would have, as a minimum requirement, a full watching of the video with an open and nonjudgmental mind. There are all kinds of reasons why someone might not want to do that, or be able to do that, and not all of them are bad reasons. But whatever the reason, if you don't start with an open and informed mind, you're not qualified to participate in a discussion.