Yeah, it's certainly not helpful when people do that.
I would think, though, that the actual videos on youtube probably have a bigger impact on people's opinions then the comments under those videos, considering how inane most of those comments tend to be. For some reason the comments sections on youtube videos seems to be almost universally dominated by the lowest common denominator.
Transhuman, a 20-minute Dutch documentary about Anders Sandberg, is now available online. From Sandberg's blog:
The documentary features Nick Bostrom at 9:23-10:32 and at 19:28-19:37. There's also a cameo appearance of Eliezer Yudkowsky, Carl Shulman, Anna Salamon, Toby Ord, William MacAskill, David Pearce and Stuart Armstrong.