In my view the only ethical concern with violence in games is how it affects the other players at the table.
I think this is an excellent point. I'll use an example outside of gaming, as it illustrates the point.
I have a friend who is a survivor of abuse as a child, and has PTSD as a result.
This person does not have a problem with most comic-book superhero movies. The Spider-Man flicks, X-men films, the current Marvel Cinematic universe, all cool, and they enjoy them.
The Daredevil TV show, or the movie Sin City, which are also based in comic books, however, are problematic. The violence in these is... more brutal. Less comic-book-like. And as a result, tends to act as a trigger. And not "trigger" in the common current usage of "it makes me uncomfortable". I mean trigger in the PTSD meaning of giving this person flashbacks to violent events in their past.
Now, most of us (thankfully) don't have to deal with outright PTSD at the table, but the point is that different portrayal can mean somewhat more to someone than you might think, and we should be respectful of that. I wouldn't invite my friend over to watch Daredevil. I wouldn't run a game scene with a violent rape if someone at the table had suffered such in real life.
Imaginary violence may not be a big deal, as a general thing, but we can respect individual tolerances as well.