The way most epigenetic changes have been observed to work, is that information is collected by various "setup programs" (genes that activate on a timeline, and then silence themselves after "running.") These "setup programs" run only during development — usually natal development, though some of this occurs as late as early childhood. And these "setup programs" store the resulting calculated "flags" as modifications to the epigenome.
Crucially, because these "setup programs" silence themselves after running, these "setup programs" each only have one opportunity to run, at some genetically-defined point in an organism's lifecycle. The information is only collected once. Whatever this "setup program" observed at that point, that's what the epigenome records. There is no second chance to set it differently.
I don't know much about this violence finding, but one famous finding in epigenetics is that mammals whose mothers were often food-deprived during gestation, end up with a marker that correlates with the phenotype of eating more / being more food-motivated / tending more toward gathering more food than is necessary for their immediate satiation.
At least in the case of this food-deprivation finding, there is nothing you can do to/with the animal afterward, that reverses the impact of this epigenetic change. The animal's body doesn't go back and re-evaluate whether or not it "should" be more food-motivated, because the fact it's basing its food-motivation calculations off isn't about what's true now — it's about what was true then. The marker doesn't mean "the environment is currently food-poor", it means "the environment was food-poor when I was -6mo old."
(In fact, these early-natal-development epigenetic markers aren't even necessarily what you might call runtime flags — they're more like an #IFDEF statement in the DNA "codebase", their values first calculated during the long, continuous "build process" of development, and then macro-expanded later in that same build process to hard-code other things — e.g. how certain proteins/tissues and their chemical receptors get built. By the time a baby is born, that marker might actually have no further relevance, having done all its work and made its downstream impacts during gestation. If we had "epigenetic CRISPR" and turned that marker off in an adult person, doing so would only impact whatever that gene does after development — which might be "nothing.")