There are a LOT of active duty with no use or respect for Rumsfeld. And with most of the officer core Republican (roughly 90%), it isn't likely they are all democrat plants. In the O-4/5 range, I'd say about 50% dislike Rumsfeld, but that percentage is growing.
One needs to accept the possibility, at least, that some of these guys care about the US and are speaking out because Rumsfeld is not doing an acceptable job.
You either oppose the Democrats taking power and ALL of their machinations or you do not. If you do not, leave.
There is no room for equivocation. A daily mantra is ORCHESTRATED. If there were genuine motivations, the place to complain would be directly to the president. Going public, loudly, is for one reason and one reason only. To advance the Democrat strategy.