Violence is something that is primal within us. Even the most calm and collected person sometimes has moments where violence tempts them. In story settings, it can often be required to survive. Especially with all the dystopian stories, violence is often the only way for those characters to live another day, or to keep those they love safe. Despite that, we rarely hear of a story being banned from a library or school for being too violent. It’s far more common for books to be banned for sex, racial issues, profanity, or even “magical” elements. Violence is perfectly acceptable to teach children, but stars forefend that they learn about any of those other things.
I think for a lot of people, sex is taboo because we’ve developed a culture that likes to pretend sex is just something people do to procreate and that’s it. Race is a sensitive issue, because it’s not rational, and it’s almost impossible to address for most people without their own biases coming into play. That wouldn’t be a problem, if people were aware of their own biases. Most people, however, aren’t. Profanity is one of those things adults like to pretend their children don’t know. I knew all of the American curse words by age 4, because my grandfather was a sailor, complete with anchor tattoo, and he never watched his mouth. Of course, the only time I slipped up as a kid and cursed in front of someone, it was my mom. She tried to wash my mouth out with soap, but I was crafty. I pretended it tasted good. She never tried that punishment again!
Violence is glorified in our world. Can we even imagine, even as writers, a world without it? I would love to see a truly alien race, who considers violence as unthinkably taboo as we would people having sex, in public, while yelling out profanity laced, racist slurs that also disparage religion. And yes, I did have to fit that all in one, lol! What kind of world would there be, where there is no violence?