Why do child-targeted and sexual crimes carry a heavier stigma than other inhumane crimes in the USA?

Not a loaded question, I'm not accusing the USA of anything. It's just that I'm not familiar with the laws in other countries. What does happen in other countries, though, is that even murderers will gang up on child rapists in prisons. I wonder why there is imbalance in injustice when all three of those seem pretty bad.