This was the top post when I checked Lemmy this morning.. Mod commented to mark the post NSFW, even though it wasn't NSFW as far as I could tell. Post was locked and had a ton of deleted comments.
That's because you're not thinking about everyone else. The question is what message you're sending to the listeners.
If you choose a word (like "retard") which is discriminatory, you're showing your hate for the minority group, and not just for the other person. And that has an effect on the community at large. Maybe they don't want to be surrounded by bigots. Maybe they think that's shit.
So, if you're gonna have a flame war, pick negative and non-discriminatory words like "jerk" or "fuckface". Or don't, and get banned or blocked, if the mod feels like it. Either way.