I am glad someone made a thread about this. Honestly, going through what the spoiler discussion was like at least, it was pretty bad.
I wouldn't take the "Zoro is one of the most hated" guys seriously. Just take a look at the spoiler discussion. Like half of the posts are Zoro wank posts. Moreover, Sanji is crapped on weekly because there is more material to work with - it is doubtful that he is less hated than him.
If anything, Zoro fans are among the most aggressive and spammy, and people start hating the Zoro fans rather.
Admiral fans have been pretty bad lately too. I mean, the image of Kizaru sticking a light penis into Kaidou's mouth is kind of gross and feels like Robot Chicken material.
Admiral fans seem to be a "traumatized fanbase lashing out" on some level. On their defense, people were calling Green Bull "Green Bitch" back at Wano end, and the term "Assmirals" and "Pissmirals" are now common place.