Murder is accepted and even normal in most games because of the safety of the context provided within them. When you're playing a criminal, a soldier following orders, or a good character charged with the task of eliminating bad guys, it's all okay for most people to accept. We watch film and television that regularly has made violence a core element of its storytelling and entertainment value for many decades since WWII. People are generally fine with that. What we don't do is watch rape or simulated rape because there's never a reason for it in the context of a game. What reason is there for rape being displayed so upfront? Why make the player complicit to such an act and witness something that has nothing to do with their goals? Games and literature/film are different enough that it should be necessary to understand that reading about or viewing something is different from playing something that makes you a direct part of the experience. Does it matter if murder is worse than rape when one is given context and the other isn't and, on top, does not fit with our sensibilities? No one's going out and wasting people like a video games unless you're some kind of messed up individual to begin with, but do we need a reason to witness or imply the act of rape when there's simply no game-value for it? Murder in games is a more abstract act that fits within a well-understood and familiar theme seen in literature and film and even gaming prior to video games. Rape has no value in entertainment such as gaming.
But the context is this guy is a psycho criminal who does anything and everything evil to others, right? I mean are we talking about the context of who the main character is and what the developers want you to feel towards that character or not? If the context is there, why is there absolutely no place ever in gaming for rape specifically but other violent acts that earn a criminal more jail time are completely ok?
They want you to hate this character, but since many gamers are completely desensitized to brutal violence, the developers had to take a different tact in order to have those gamers hate the character.