Should have done this in the first place.
The original Human Rights Watch report can be found here.
Those of you who don't swallow MSNBC's stuff like a carp gulping down a hook are welcome to check it out yourself.
The term "political opponent" tossed off so easily here is a little more complex.
The first category comprises twenty-one people apparently arrested for their alleged affiliation with an armed group or an opposition political party or for reasons of state security that may be related to their political party affiliation. The legal authority for such arrests was not specified.
In cases investigated by Human Rights Watch, such persons were detained by the police or the intelligence service for an indeterminate period and then released without the case ever reaching the courts.
Human Rights Watch’s investigation of these detentions focused on suspected members or sympathizers of Shi’a cleric Muqtada al-Sadr’s Mahdi Army (Jaysh al-Mahdi), an armed group established in June 2003 in contravention of CPA regulations governing armed forces and militias in Iraq, and of the Hizbullah Movement in Iraq, a political party established in Iran in 1982 in opposition to the Saddam Hussein government, and which abandoned armed opposition following its return to Iraq. Human Rights Watch interviewed most of these persons after they had been released from detention without having been charged.
More details on these arrests can be found beginning on page 29.
The report gives you the chance to look over details of the interviews, and decide for yourself which might be credible, and which are less so.
In other words, the Rest of the Story.