I think 99% of people on HN understand exactly what you mean by privilege here, even if they don't agree with its implications. But I would ask you to consider that telling people to "do some homework" reflects a certain privilege that liberals have in certain circles. In particular, the privilege that goes with not having one's views challenged (again, in certain circles), and therefore assuming that it is your job to educate everyone else. I certainly don't go around telling people to "do some homework" if they haven't heard of the welfare theorems of economics, even if it would be very useful for them to know it.
In my opinion, what he did was completely appropriate, not condescending, and helpful and I wish you wouldn't have just blindly classified the action as a liberal tendency.