Because that series, at a glance, looks like it's letting people follow the Yuki of The Disappearance of Haruhi, but she acts very differently. I'm sure many people really wanted Kyon to choose Yuki and her world when they were watching The Disappearance of Haruhi and then, when it looked like that's what they were getting only for it to not actually be what they thought, it felt like a betrayal. That probably falls under "waifufagotry excepted", but that's the only thing it seemed to be looking at the tin, and that's not what fans got. Of course that hurts. After all, there are plenty of other moe shows around, there's no need to remind people of the character and world they lost by showing them an imitation of it.
Anyway, explanation/rant finished. I'm just gonna keep enjoying these nice pictures of Yuki.