How we react to things in movies and how we react to them in real life are two different things.
Hi.
Firstly, yes, as the heading above implies, its because what happens in the movies/films/cinema is not even REAL, at least, for the very MOST part ANYWAYS, and also, in real life, besides there often being legal action and real consequences to follow, in film, we don't have to personally deal with whatever consequences or aftermath that may happen, including de-facto suffering victims in cases even outside of, but also including, murder.
Heck, in real life, even LESSER acts like bullying, hitting people, stealing, damaging their stuff etc, is ALSO considered de-facto unacceptable and wrong and in its own way, it often can be and IS taken seriously.
Plus, no matter what the subject matter is in cinema, or even the existence of disturbing scenes as such, in movies, even if *occasionally* I might get a "little" fixated or in a state of trance or sensationalism out of slightly unusual even if still disturbing movie scenes, I can often find and often DO, something ELSE to appreciate or admire the film for. That includes its cinematography, pacing, acting, direction, script and screenplay, attractive actresses (haha) to enhance certain moods and scenes, a message, dark or otherwise humor and sometimes just the film ITSELF.
Yeah, sometimes people can't help it. In other cases, people may find it acceptably or even RESPECTABLY disturbing, certain films and scenes, including action films with lots of shootings and killings, horror movies with lots of gore and shock value etc and even controversial shock fests ala Pasolini's "Salo or the 120 Days of Sodom" (1975) etc to give ONE extreme example. And yes, audiences DO exist for THAT kind of cinema too.
And in certain revenge themes movies, people can get a catharsis over seeing evil beings punished for inflicting deaths and suffering on innocents. Even HERE I can appreciate films for OTHER things too, but again, if subject and approach wise it satisfies audiences, why not? (Although some films STILL receive controversy here...)
Anyways...