Rape is NEVER about the sex. It's forced sex as a means of control.
This has been known for years, now. There are sex crimes which are about the sex, but they're generally of a lesser class.

In rape cases, it's the mental wounding that is never completely healed, or almost never, and when it IS healed, there are deep scars left on the psyche.

I don't know about castration, as a means of stopping this. There are some for it, but medical studies have shown that it doesn't drop the testosterone levels significantly enough for quite some time. So maybe, say, castrate, then 5 years in prison, while the levels drop?