Calling members of the military "cowards" is fine. There is a tacit understanding many members of the military have come to and that's that you can't please everyone. What is more insulting than seeing this man being called a "coward" are the people who believe they are patriots by seeing a film and expressing a pro-war mantra.
Since 9/11, more than 10,000 U.S. children have lost a parent, sibling or other loved one who served in the U.S. Military. There are several organizations dedicated to start the healing process and to provide care and support to family members -- including children -- who have suffered the loss of a loved one serving in the armed forces.