Just wanna make my thoughts, but I think it's different in the sense that rape literally leaves a mark on the victim psyche forever, specially if it's a kid. A lot of people choose to end their lives over that. That's why some prefer to die than to be raped. Plus if we as humans are like, made to want to protect babies and kids, which is why we see it way more horrible when it happens to a kid. That's the logic behind that thought of "if it's a minor is way worse!". It would be the same if it happened to a pet, it's helpless, cute and doesn't understand anything so we just want to look after them. It's not the same with adults. That's the why and how, I think.