The number of times I've been spoiled for looking up a characters r34 page is not 0.
Usually it's a transformation, haircut, new outfit or lost limb, but sometimes you can be spoiled about deaths or the bad guys joining the good guys.
...no? This is specifically referring to things like fanfiction. Haters rarely actually write fanfiction - you'd have to be really dedicated to despise a work enough to devote hours of your life to writing in its universe. Fanfiction is generally quite earnest and made with love for the original work.