What is amazing to me in this whole "obstruction" debate is how quickly the grants of immunity to 5 key people in the Clinton email investigation have been forgotten. Mueller used a common prosecutorial tactic in bringing charges against key Trump associates, and then using that as leverage to get cooperation against other witnesses. But in Hillary's email scandal, Obama's DOJ did the opposite. They granted immunity to five Hillary aides most likely to have committed criminal acts, which meant that not only could they not be prosecuted, but none of them ever had any incentive to turn on Hillary. Obama's DOJ deliberately torpedoed the investigation into Hillary's emails.
