Okay, I agree that some drug crimes (possession of a dried plant?) do not really rise to the level to require federal incarceration.
That being said, these prisoners are now, by a and large, hardened criminals, made that way by the Federal prison system. Releasing them is only going to increase the level of chaos in America.
Maybe that's what Obama wants. Maybe with enough chaos, people will BEG for martial law.
...And you ain't gonna like the normalization part.