There are some important differences however. The President is elected by the people. He is expected to to watch out for out best interests and take the country in the right direction. As such, he holds his position only at by the collective voice of the people. That makes him a public servant. He reports to us. And is supposed to hold himself accountable to us. Not only is it our right to criticize him, its our duty to call him on things that we dont agree with.
A soldier however is not in the same catagory at all. We do not vote for soldiers, and we have no say in what soldiers do. The military carries out the orders that come down the chain of command and they are only held responsible by those above them in that chain. We can rant and rave all day long but whatever eventual punishment is decided upon, will come from within the military. You can criticize them all you want, but what Apdst is saying is that until you are a soldier you will never understand them.