This video seems pretty pointless. He makes the claim that historically, people have been wrong about essentially all of their beliefs. That seems wrong--most people's beliefs are things like "mountains are tall", "my knee hurts", or "there are fruit trees in this valley".
He also assumes that we are not in a "more privileged position with respect to the Truth". But obviously we are, at least to some extent. Someone who only only has access to the data they collected from the first day of an experiment knows less than someone who collects another day of results and can read the first person's notes.
Overall, there just isn't anything in the video that makes it worth watching, especially for people who spend time on LW.
I'm new to the community so I appreciate your willingness to explain the poor reception this video got. That said I think the point you critique is still valid and that you might be less critical if you'd watched the last 5 minutes of the video. Are we in a "more privileged position"? Yes, and he acknowledges that towards the end. However, "more" is a relative term. In all likely-hood a thousand years from now scientists will look back and say we were less wrong than we had been in the past but still far more wrong than they will be. I...
https://www.youtube.com/watch?v=E8V8rtdXnLA&feature
Be sure to make it to the last 5 minutes of the lecture as the tone shifts significantly.