You are right to say that it's possible to have extemely harmful blog posts, and it is also possible to have mostly harmless blog posts. I also agree that the examples you've cited are apt.

However, it is also possible to have extremely good blog posts (such as one containing designs for a tool to prevent the rise of UFAI or that changed many powerful people's minds for the better) and to have barely beneficial ones.

Do we have a reason to think that the big bads are more likely than big goods? Or that a few really big bads are more likely than many moderate goods? I think that's the kind of reason that would topple what I've said.

One of my assumptions here is that whether a post is good or bad does not change the magnitude of its impact. The magnitide of its positivity or negativity might change its the magnitude of its impact, but why should the sign?

I'm sorry if I've misunderstood your criticism. If I have, please give me another chance.