People aren’t always nice, kind, or respectful — even the people who love us. We’re careless with our words. We react emotionally, blurting out whatever comes to mind rather than taking a moment to think about the impact of what we have to say.
If I were crazy, where would I have put that? That’s the stupidest thing I’ve ever heard. What is your major malfunction? Can’t you read? Are you an idiot? What’s so hard about this? Why can’t you follow instructions?
In the real world, everyone reacts differently to hearing things like this. Some people can forget them. Others remember those words for years. They’re almost never followed by an apology. Usually, the speaker forgets saying them at all. Try to bring them up later, and you’ll be accused of mishearing or flat-out making things up.
Miscommunication happens. Cruelty happens. Insults happen. And realism in writing is good, right? So why not write those things in?
The problem is, when someone is reading dialog — when those words are on the page right in front of you — the specific words stick with the reader. Even if the dialog is meant to be spoken outside the other person’s hearing, they can’t be un-read. It’s damned hard to forgive a hero or heroine who says something so rude or disrespectful under any circumstance.
One of my readers once told me that, when reading a romance, they wanted the love interests to be kind and respectful to one another. It’s hard to fit cruelty, no matter how realistic, into that sort of respect.
This can be done in a hate-turns-to-love romance, but it requires a careful touch. Otherwise, the reader’s never going to believe that Love Interest #1 would forgive Love Interest #2 for all the crappy things they said three chapters ago.
And these types of lines can certainly appear in a fight scene, when tempers are high, but they’ve always got to be followed up with an apology or reconciliation. Pretending “it never happened” might work in real life (protip: it doesn’t) but it usually won’t work on a reader, no matter how you twist and contort to make the characters accept it.
In any other romance trope — especially if the hateful things are coming after the relationship is established — it’s even harder to include insulting dialog without breaking the reader’s suspension of disbelief or making the reader hate the characters and ask, “Why are these two even together?”