The problem is that the sentencing guidelines are too lenient in the first place and that laws are too lax generally.
Personally I'd operate a "three strikes and you're out" rule - commit three crimes, and you are executed. It would mean that scum like this rapist are never released and still give someone who has made a couple of less serious mistakes the opportunity to change.
As it is, he has served the minimum sentence he was given so he has to be considered for release.