Besides, Glass volunteered to join the National Guard and he needs to accept the responsibility that entails.
America is not a country where he will face harsh treatment. He’ll probably even get a movie deal out of this and do the talk show circuit for the next year or so.
Quite simply, if Glass was a true man of principle, he would go home and face his fate, whatever it may be. Otherwise he simply looks like a coward and someone trying to shirk his responsibilities.