When generals and admirals begin to resign their commissions in protest, or refuse to carry out orders, then you can talk about a "revolt." See "revolt of the admirals," for example.
Retired generals (or Navy reserve captains for that matter) are citizens. As such, they have the right to express their opinions freely. But they are simply opinions. See Smedley Butler for an example of a man whose post military opinions were freely expressed.
UPDATE: I've read a lot of commentary on the generals today but I really like this part of what The Shuteye Train wrote at InstaPunk:
So what's different about today? We have a bunch of major generals -- retired, and therefore not subject to military discipline, inflated with all the omniscient ego of a soldier who doesn't have to engage the enemy ever again -- who object to the absolute authority of a civilian who didn't spend thirty years kissing the asses of those who happened to graduate ahead of him at West Point. And they have a terrible story to tell about how their brilliant advice was rudely rebuffed by a Secretary of Defense serving at the pleasure of a President who actually dared to go to war. What could be awfuller than that?
Here's what could be awfuller than that. A corps of generals who could run roughshod over the civilian command of the military. All we've learned from the temper tantrum of the past few days is that generals don't like to be told what to do. Particularly by a Secretary of Defense. Today the NYT seems to agree with them. But ask yourselves this: If we hadn't renamed the office in the peace-loving aftermath of WWII and if it were still titled Secretary of War, how we would you feel about generals wanting to bully the Secretary? But the dirty secret is, they didn't want to take orders from men in mufti even back then. They've always thought they were above that. They aren't, but it's the danger they've posed to every government in history from Rome onwards. The absolute supremacy of the civilian government over the military is one of the great points of genius in our Constitution. It's why the government of the United States has never been seized by a general, not even Douglas MacArthur. But, by the way, does anyone remember the name of Truman's Secretary of Defense? No. Truman had to fire MacArthur himself, because his SecDef was too much of a wimp to do it himself.