I belive that the Downhill Thread was created by a fan who was worried and had gotten the "wrong" view of due to the fact that to him/her it seemed like Ayu is going downhill, rather than someone disliking her. Due to various facts that really indicate she does go downhill, in a way. (sales)
imo the thread wasn't unneccessary because it let people air their thoughts, a lot of people probably broadened their view on the matter after reading in that thread.
I agree that the thread had a negative tone in some parts of it, but that's not something that anyone should be too bothered by
.