First, I second what kb said re: "so much worse than other crimes." I don't know of anyone who's ever been granted the death penalty for rape, and that's for sure. On to my next point: of all things in this world in which we live there is no thing more innately a person's than their own body. A house isn't me. A car isn't me. You can rob my house or steal my car and I will feel like you are attacking me, but it is removed from myself and more importantly, from who I am. Anorexia and other body image disorders are often related to control. It's no coincidence that many rape and assault survivors, especially among women, develop disorders like anorexia and bulimia after they experience assault. Your body - that thing which is the only thing in the world completely, 100%, inherently yours and no one else's - when you are raped or assaulted, someone else literally takes your body, that thing which is supposed to be yours, and says "Nope, that body? I'm going to make it do what I want. It's not yours. That thing in which you live? It is a shell, and I'm going to make it mine." Rape is an ultimate act of disempowerment and lack of control. Unlike killing someone, the person who is raped has to survive afterwards - so while you could say that when you kill someone, it's an ultimate act of disempowerment, it's not like anyone has to live with the feelings that spring from that act afterwards. Think about those things. Also I just read an r/relationships post about "feeder relationships" and "feeder fetishes" and I'd agree that forcing food down someone else's throat so long as they are not at risk of imminent death due to starvation is abusive as well. I honestly have struggled in the past with things like "Can we really tell someone who cuts themselves not to cut themselves? Why?" due to body ownership things. I have mostly come down to "We care about people and do not want them to hurt themselves and some ways that people clearly hurt themselves we have decided it's okay to try very hard to stop them."
The death penalty has been given for rape, but mainly in developing countries. There was a man killed a few years ago for it in Dubai. Anyway, I think your response covers the reasoning pretty well. Just to build on it, I think it's also a crime where there really can be no excuse. You might kill someone in self defense, or for material gain. You might steal because you owe someone money, or you might be starving. On the other hand, rape is someone behaving like an animal, like no functioning member of society should behave. It's an act of someone completely devoid of humanity, which I think is another factor in why we find it so abhorrent.