McChrystal's comments, as detailed in the Rolling Stone article, do "not meet the standards that should be set by a commanding general," the president said today while announcing the switch. "It undermines the civilian control of the military... and it erodes the trust that is necessary for our team to work together to achieve our objectives in Afghanistan."
The president praised McChrystal for his "deep intelligence" and "love of the country," but made it clear the comments McChrystal and his aides made could jeopardize the U.S. mission in Afghanistan.
"All Americans should be grateful for Gen. McChrystal's remarkable career in uniform, but war is bigger than any one man or woman," the president said. "I believe it is the right decision for our national security."
Obama said the change was needed to maintain unity of U.S. efforts in Afghanistan and to "hold ourselves accountable to standards that are at the core of our democracy." The president reaffirmed that the change in personnel didn't mean a change in U.S. policy.
For me, the key statement in the President's speech was when he said "disagreement is fine; division is not."
UPDATE: President Obama spoke today in the Rose Garden about McChrystal and Petraeus: