YouTube is a unique site. You have this wonderful collection of every kind of video you can imagine and it's a place you could waste all day on. But right below those videos are the comments and "You will never find a more wretched hive of scum and villainy" and trolls.
I think the only thing you can do is turn off comments and then have a link which would lead the viewer to a blog where you'd have much more control over commenting.
That does sound a bit convoluted, doesn't it?