True enough now....but not necessarily during a prefabricated crisis.
All Obama has to do is create a crisis by passing a very high firearms license/tax. Enough to start a few high profile Lexington Green's part two: Say in Waco or Ruby Ridge or Eldorado or the like.
As soon as people start firing on National Guard or such, well, the Army is going to do their duty to restore order under the constitutional authority of the POTUS whether they agree with him or not.
It's not as simple as just saying the Army are moral, ethical, professionals.
Those positive qualities could perhaps be used jujitsu style.
The SCOTUS weighed in on the 2nd amendment when they handed down the Washington D.C. gun ruling. Officers are aware of the ruling.
Especially when the Usurper grants people like Wesley Clark supreme command.