To anyone with an affiliation with the military, this is completely expected. In fact, I am surprised that they didn't try to get him with being AWOL for refusing to go.
He knows (or should know) that having submitted to the US Army, he is subject to deployments wherever they need him, not necessarily wherever he wants to go. If soldiers could choose where they wanted to go like he was trying to, there would be a hell of a lot less soldiers in harms way that wanted to be able to come home to their families.As for the
He was taught by the military, just like every soldier is taught that you cannot make political statements of any kind while representing the military, because it can be construed as a statement by the military. As a soldier he is alllowed to deal with politics, but he cannot associate himself with the military while he does it.Unfortunately this means that as a military member, he loses access to certain rights and privileges that are available to the rest of the American population, but he also gains several that compensate for those losses. All such losses are pretty much understood when the person takes the oath to become a service member.