You are doing it again: Confusing your moral code with a general statement everybody has to use. I already said that if the narrative is conclusive and does neatly explain it, nearly everything is possible in fiction. That is one reason why people love fiction. The topic of "enemies to lovers" wasn´t invented by me, but it is rather pretty common. And often used in general media, but also in fanfiction.
Not to say even if it may be not realistic in some stories, people can still ship it, since it is only fiction.
Actually I don´t take it personal, but I don´t like it if a person confuses their own opinion with general facts. This is a forum and we both are part of it. I am not shy, how you could very well see and therefore I write to you.
Fact is you stated it as a general fact: "Those who want a Yona x Soo Won, must like toxic relationships."
The way it is worded, shows that it is not a personal opinion, but stated as if this is fact.
Therefore I only mentioned that it is nice that this may be your opinion, but you should please not state is as general fact and judge people based on them shipping certain characters together.