The following excerpt from that interview contains the complete comments of the President on sentencing and drug policy.
Some people deliberately hurt other people.
And they ought to be in jail because they can't be trusted to be on the streets. Some people do things that are so serious they have to be put in jail to discourage other people from doing similar things. But a lot of people are in prison today because they, themselves, have drug problems or alcohol problems. You know, I have some experience with this. He was lucky to live through that.