Nixon and Kissenger were/are sociopaths.
http://www.bbc.co.uk/news/world-asia-16207201
The news of the genocide was reported by an West Pakistani reporter. He would later become the first reporter to break news of Pakistan's nuclear status.
As you have stated, nixon was wrong on a lot of things. Nixon stating the army wasn't involved is negated by more eye witnesses and journalists from around the world. Hell, the blood telegram was completely ignored by Nixon.
Please go ahead and read: https://www.amazon.com/Century-Genocide-Critical-Eyewitness-Accounts/dp/0415990858