Yes, lenience with criminals leads to more crime. A criminal should face a jury and should then be rehabilitated. If the criminal is not rehabilitated, he or she will only cause more damage once released. There should be programs in place to help those who have committed crimes overcome their past.
Yes, lenience with criminals leads to more crime, because the criminals don't learn that the behavior is unacceptable. They learn that at best, you get a slap on the wrist and some treatment. Ultimately, the criminals offend again because they didn't have to take it seriously the last time. This can lead to tragic results such as in Greene's situation.
Lenience with criminals leads to more crime. It's really no different than dealing with your kids. If you don't send a clear and ample message, then expect more of the same behavior, or worse as the offender pushes the limits of what he or she can get away with. Punish harshly early and often and you solve a lot of problems. More of a problem is that our precious little snowflakes can't stand to be punished.
Prison is a great way to turn someone into a career criminal, for several reasons. The first is that prison give criminals access to a network of other criminals. It also teaches them that they have no hope, and a life of crime is all they can do. It also teaches them that they can live through prision.