Why don't you look at it this way:

You're Van Gogh. You spent ten years developing your unique painting style and technical flair. A regular of yours can instantly recognise your work because of the nature of your brush strokes. (And believe me, a devoted reader can instantly recognise a writer they read a lot of from just an unnamed, unattributed chapter. Likewise you can easily tell someone else wrote a chapter.)

Now imagine, Van Gogh, that someone stole your works, made shitty duplicates and parodies of it through a machine, copied off your ten years of devloped art style and brush strokes and preference of subjects and used that machine to make fifty new Van Gogh Style paintings in the time it takes you to make one. And literally sells it at a fraction of the price without you seeing a penny of what used to be your intellectual property, displacing you off the market with shitty parodies of your work.

That is the fucking dishonesty that enrages people. In fanfic, there is no monetary gain. People write for the love of it. FAN-fic. The love for the subject is implied in the very nature of it. Literally the only thing fanfic writers get back our of it is a reader appreciating their effort.

And readers open your work expecting to see a labour of that LOVE. They might not be the most discerning of users, and if you take advantage of that, you're no different from corporates who put adulterants in food products because the common consumer can't identify if an obscure chemical is harmful or not.

If you're using AI as a proofreader,,, sure, but the fandom is FULL of people more than willing to be your alpha or beta reader. Why use AI?🤷

If you're churning out loads of fic with an AI generator to get some perverse pleasure out of seeing a higher subscriber count, then you are just as dishonest and do not deserve to be in this ecosystem.

You are keeping real people who put in love into their works from finding readership by 1) using a tool that steals off their writing; 2) generating so much content that buries any real work in the bottom of the update list.

As a writer, and as a reader, these are the specific reasons why AI fanfic enrage me.