I saw that. It was already quoted by someone else earlier.
I have read it!
One case is left out!
What if the content is legal but a group of people start claiming is illegal
and submit hashes around gray listing legal content?!

Well all greylists would be community run and you'd have to opt-in only to the ones you trusted (which would, ideally, be validated as correct by many community folks). If you don't trust them you don't have to use those lists (or any, for that matter). The blog post (and other posts on storjtalk.org) and our FAQ go into much more detail about questions that come up regarding this too.