Do you want those who improperly classified info to be punished, as well?
As that is neither a violation of oaths, nor military code, nor US law, I think the appropriate response is to determine who is at fault and hold them accountable through the normal democratic process.
Actually over classification is a federal crime. The same law that set out the classification levels etc also made it illegal to knowing over classify material simply to keep it out of the public eye. Now that aside I still feel from what I know what Manning did was wrong and he should be punished to the full extent of the law.
A computer without COBOL and Fortran is like a piece of chocolate cake without ketchup and mustard.