Hrm, I see what you're saying, but as a rape survivor, I personally disagree.

However horrific it is, rape is survivable. Murder is not, and I'm happier being alive. And with healing, the suffering from rape can be overcome.

I think the reason we perceive sex crimes as worse than murder is that most of us can perceive situations where killing someone is morally justifiable. Very few can think of a situation where raping someone is morally justifiable.