Video games and the discussion around video games always seem to have such limited vocabulary when it comes to this kind of thing.
Here's the first thing: as with any narrative/art, nothing should really be off the table. You can explore everything and anything, as long as you do it with care and respect, especially when it comes to the more controversial/sensitive topics. Rape is a very sensitive issue that, when explored appropriately, can contextualise experiences, condemn actions and bring relief and understanding to victims. This is valuable, and it'd be silly to say "there's a rape scene in x... that's bad."
With that in mind, as Rockstar often does, they dive head first into extremely sensitive topics and handle it with about as much grace as a bulldozer. Having a throwaway moment where amidst hunting, looting and riding you get fucking raped like it's just any other day. "Oh my god" and then go back to your business without any followup cause and effectual response is so lousy, lazy and Rockstar-esque I don't know what to say at this point.
On top of this, we've got posts in this thread saying "I mean, this game's filled with murder too" and I completely agree. But I imagine the implication of such a statement is meant to be taken as "there's violence all the time in games, it's an adult game, so why should rape be any worse?", which is disingenuous. This isn't a moment to let both rape and intense violence off the leash. Rather, I see it more as "How did we reach a point where such extremely graphic and sadistic violence is normalised in video games?" Both rape and murder are disgusting and sensitive acts that should be treated with extreme care. Unfortunately extreme ultra-violence has been around in video games for so long that we don't even bat an eyelid to it and that muddies the waters going forward with other sensitive topics.
This is a wakeup call that video games as art have a responsibility to handle their themes and content with care, and they seldom do. You can't handwave this as "adult content." Adult content also means adult approach to adult themes. Blowing someone's head off and then going about your day like a sociopath raises my eyebrow in the same way this rape scene does and if you are disgusted by a throwaway rape scene in a video game, maybe you should look hard and consider why murder and ultra-violence is any different besides the social conditioning you've experienced growing up.