1.There's a concept of realism in video games. Not reality, but realistic. For starters, those 7000 spawns will be killing innocent Baldur citizens, and a "good" hero can also kill those 7000 without ascending Astarion for that very reason. And speaking of empathy, a lack of empathy for someone outsider is in no way correlated with a lack of empathy for the person closest to you, much less the person you've been through all of this with. It is NOT realistic. And in a huge number of movies, books, the relationship of an evil couple is shown realistically. Where is the sadistic porn shown in Joker and Harley Quinn's relationship? Where does Harley have the eyes of a victim? Is the Joker much kinder than Lord Astarion, sympathizing with everyone?
2.There is a huge difference for a person with empathy to perceive between some victims in the story of the game, and specific shots where we are shown a video of the rapist abusing the victim, in detail, with all the facial expressions of the victim of sadistic content. Also, at no point in the game's storyline does Astarion take control of Tav, only and exclusively in these scenes. Irritation at spiders is an individual phobia, and not wanting to see scenes of sexual violence is something that is inherent in far more people.
3.Please provide specific facts from the game, story-wise, from which such content would logically follow. Make it clear.
Apologies if some of my answers aren't exactly what you meant, I think you're using a google translator and it's hard for me to fully understand what you exactly meant.
1. You can kill them but still not condemn them to eternal torture. Big difference. Also, they're not attacking Baldur's Gate citizens, because they're going to the underdark. It's worth noting that they seem to be doing well judging by the epilogue note, although we don't know that at the time of the ritual, so fair enough. Joker and Harley aren't a good example when it comes to fetishizing abuse or portraying her as a very graphic victim of abuse. There are famous instances of JokerxHarley dynamics doing so. Her first iteration was depicting her being horribly physically assaulted and battered by the Joker. One of the most famous iterations (the original Suicide Squad) glorifies their abusive relationship.
2. Not wanting to see gore is also inherent in a lot of people (perhaps more). Yet the game depicts it gratuitously and often. Censoring certain themes isn't a good idea, IMO. There is a lot of body horror. Also, Astarion doesn't allow you to leave if you try to break up, so I'd say that's another instance of controlling Tav.
3. Assuming you don't care about the devnotes (again, writer's instructions for Neil) I attached that outright refer to him as abusive, Astarion's entire story is about how abuse has affected him and whether or not he will go on to inflict it on others in order to maintain the feeling of power. In act 1 he's already describing vampire lords as inherently abusive ("paranoid power-hungry creatures" "a spawn is their obedient puppet" which can be nicely contrasted with "you're going to be wonderfully obedient" etc) a couple of lines where he implies or more outright says he wants to be like Cazador (that one conversation where he says he's jealous of him, the power he commands and the miracle he's on the verge of, and him outright recognising this in the spawn Route). He terribly lashes out at origin Karlach if he tries to turn her in a way that's actually much more triggering for me than the kisses, he doesn't let you break up with him in the ending scene, he, in my opinion, sincerely states he would have ruined your love until you were nothing (a bluff about this doesn't seem to make much sense to me)... There are more, but these are so often debated and people are so wilfully interpreting what they want to see that I see no point in bringing them up. One of my controversial takes that I don't see brought up often is that the epilogue line where a Tav that doesn't want to be with Ascended Astarion complains about freedom, he specifies that he gives them "pleasure", which, considering that this Tav doesn't want to be there, might be implying sexual abuse. This isn't necessarily what the writers intended though and might just be my reading of the line, but I don't think it's a too out-there reading. I will say I already saw the crux of Astarion's arc back when I played Early Access, and correctly predicted his evil ending would be him becoming a Vampire Lord (didn't predict Ascension) and turning romanced Tav into a spawn that he would degrade.
Btw, funny that we both brought up Joker and Harley, I promise I hadn't seen this when I wrote that other reply, lol