He may be progressive, but he is not a liberal. The two terms have different meanings. A progressive person advocates changing a norm--the opposite of conservative. A liberal advocates personal freedoms--the opposite of an authoritarian. Obama is as tyrannical in his foreign and domestic policies as Bush had been. Either Obama is a villain too or presidents are not really running the show.
I would like to think Obama is allowing this to happen because he lacks the experience to feel that he can stand up to an army general or an FBI agent. These are rogue agencies. What Manning is undergoing is torture. Since the US government destroyed Habeas Corpus in the last decade, a person only has to be arbitrarily labeled a "terrorist" to have no rights to a trial or even charges levied. I do think the government has a loophole in that Manning is an enlisted soldier and not a civilian. Soldiers in the army are the only citizens who willingly forfeit their full rights under the Constitution. I have seen soldiers held in non-judicial confinement, though not for years!