ZKK itself as theory was fine at the beginning. Way over the top in my opinion, but everyone is biased his own way, so fine by me.
What made it toxic are some specific users which tend to insult everyone not agreeing with it. Also they spam the ZKK stuff in every thread, even tho it has nothing to do with it or Zoro itself. Just look at the spoilersthread every damn week. They cant stop intoxicate the threads every week.
But thats not it, they even create more ZKK threads on a daily basis and tag alot of people in it (like me) which already said dozen times they dont want to get tagged. So some user force alot of people see these topics daily, which starts to annoy pretty fast, specialy cause these threads are 9/10 times the same with different wording.
So these users, not the whole Z fandom for sure, annoy alot of users on a daily basis with the same content, which they dont care. They disturb nearly every discussion with this ZKK theory and even get insulting if the user dont agree.
This makes the theory on a long run very toxic.