It's not because it's fictional that you can say and draw everything you want. It's not because they were not real persons harmed that you can show the more hateful and immoral things in your story. Words and pictures have meanings and can be more harmful and impactful than any physical actions. This stupid argument and the other "people choose what to read" are the things that lead us to have story (manga, anime, BD, comics ....) that show and spread harmful ideas that actually hurt real people.
And in this case, there is nothing to justify the choice of actor to show little children being abuses and one of them impregnate by her dad ? WTF !
You believe video games cause violent crime,the lesbian comics are making all Catholic girls into lesbians,rock music creates delinquent degenerates,movie ratings aren't biased,cartoons are for children only,and that fictional depictions of lolis need to be protected under child laws instead of using the resources wasted on presecuting lolicons to catch actual creeps whilst protecting real children.
Gatekeeping people from interacting a piece of media,sure,but gatekeeping the media creators themselves?
The whole premise of fictional works is to showcase literally anything,and to make a nice sum of wing wings from it.
And making that sweet dough from showing the aftermath of a fictional girl getting railed by her dads' choo choo train means that there is a market of people who want to see more of this,more dramatic stories about this,and plenty wish to see how it ends.
There's no need for anyone to justify anything beyond the simple action of storytelling and making money from fiction.