My dad was also a Marine...veteran of WWII and Korea.
He fought in the South Pacific. When I was young he used to have nightmares that he was having hand to hand combat in a foxhole. The Japanese were brutal as they swept through China and other places in their bid to take over lands. Remember that they bombed Peart Harbor and that is why the US fought them.
Others of the Armed Forces liberated France and other countries from Hitler, who wanted to establish himself as dictator (sorry, Ceasar) over the "Holy Roman Empire." He was willing to stop at nothing. I am sure the six million Jews and others in the concentration camps did not view the American soldiers as murderers, rather as those willing to stand up for justice and stop this madman.
Today there are other enemies who wish to enslave Americans to their ideologies or just kill us because we defend liberty.
For over thirty years, I did not tell my dad that I was proud of his efforts to keep America the land of the free....now I wish I could but he died before I left the WTS.....