Males were taught at a very early age how to use a gun and shoot straight. The flag symbolized freedom and all that freedom stands for. This movie makes that very clear. Some people were injured and many more died for the cause of freedom, duty, and protecting their families. War is bad.
War kills people.
No sane person likes a war. Throughout our nation's time line, war, as objectionable as it is, may be the one and only effective option for a nation to become free and remain free. No discussion of low self-esteem or silly excuses in this movie. Love your country. Protect your country.