The problem is that YouTube is a monopoly in online video. We wouldn't even be having this discussion if there were other viable providers for online video hosting. However, there aren't. So we're down to either complaining about YouTube blocking videos where it shouldn't or defending YouTube on the grounds that they're a private corporation and they have the right to host or not host whatever they please.

Moreover, I've noticed a certain ideological favoritism on Hacker News towards Google, Facebook, etc. I strongly suspect that if it weren't YouTube, but rather Comcast that was filtering these videos, the community's reaction would be different.