No it's not. The UCMJ is unique to the military and when you take the oath "to support and defend the Constitution and to obey the orders of those appointed above me" you give up your right to criticize the command structure. If you can't take this oath "freely with out any mental reservation or purpose of evasion" you have no place being in the military.
“The UCMJ is unique to the military”
But does it trump the constitution?