First of all, this idea from gamers that what you do for entertainment has no effect on the rest of your life is just not true.
What you do for entertainment has of course influence. This is not in dispute - not from me. But you do not bring any evidence that entertainment x brings about bad thing y. Search out studies, bring forth evidence. Make your arguments sound. Convince me. You can do that with sound arguments! You will achieve the opposite with unsound arguments.
What you brought was essentially wishfull thinking. You assert that playing x is bad because whatever your chain of logic was. There is another chain of logic that playing x would suppress any urges to try out x in real life, which would make games about x a good thing, would it not. You did not disprove that. I actually looked at some statistics, and the orders of magnitude between Japan and "the West" ist about 2 : 40. Let's round that down to x10 because of cultural bias. So, a place where games with such questionable content are more available has a ten times lower rate of crimes like SA. I take that as a strong hint, that your chain of logic is what I said: wishfull thinking. You think it works out that way. But it does not and might even work the complete opposite way: someone seeing/playing/reading a thing in fiction realizes that they could never ever do that thing in real life. But they still might enjoy the story or artworks or gameplay, just as we like to watch horror movies and play horror games.
Now, I am not convinced that it does work this way, but data and my own decades long experience in video games hint at it, and I want a lot better evidence than your assertions to contemplate restricting adult entertainment that consists of made up things and pixels. I have no right to restrict another person's choice of entertainment. Even if I am appaled or disgusted by it. Even if it depicts fictional things that are illegal in real life.
A person who fantasizes about raping their stepmother, or is entertained by the idea of doing so, is absolutely feeding a desire that will grow and create destruction in their life.
There is a break in logic here. You start at the point where you already have someone contemplating actual crime. You beg the question. You also equate being entertained to fantasizing about the thing. And that is why I accused you of accusing me of fantasiszing about mass murder! You assert a psychological mechanism and you assert a motivation. There is no reason to believe these things would only work for adult games.
Oh, and you also assert what feeding the desire with fiction would do. Convince me with data and not with assertions. This mechanism has been debunked for decades, which is why I am fed up with the blame-the-games-rhetoric. There is no need for video games to make people do crimes. But they are a ready scapegoat to blame. Music got the same treatement when video games were not a thing. It is the same again and again.
where the point is to just revel in the act of inflicting harm on other people is bad
... but it is not other people. You just assert that those people fantasize about doing things for real. You do not know what their motivation is. I assure you, a game without any gameplay will get boring quickly and the novelty factor of seeing realistic graphics wears off quickly. You need things like story and gameplay. What fades less quickly is the annoyance if you see signs of censorship in the game you are playing. Someone trying to impose their agenda on your entertainment. Kinda like the beeps in some audio tracks.
There do be people inflicting harm on actual people in games. But that is another topic entirely. https://en.wikipedia.org/wiki/Griefer
The effect such a game has is bad, as it leads to the normalization and glorification
You phrase this like an argument, but this is a claim. You did not substanciate this claim beyond offering your psychological mechanisms, which have been debunked decades ago. You make a step from fiction to reality. But you did not explain that step. You just assert that it happens.
Do not blame video games. Do not blame fiction. There is no easy excuses or scapegoats for what some humans do. And I am glad about anyone being able to blow off steam by playing a fictional game. In ancient Rome people would watch real people get killed in arena games. I think entertainment has bettered a lot after the rise of fictional games.