War is evil and ought not to be entered into lightly. It is somewhat boring to make that observation because everybody agrees with it. Yet looking at history forces me to conclude that we would not have been able to build our civilization without engaging in this evil a few times. And I think our civilization is one worth celebrating - certainly it has made a dent in many of the other evils that have plagued mankind since the first ape dared to walk upright.
Moreover, it takes courage to enter into the armed forces and be one of the people who sacrifices their personal goals to protect our civilization. So we have a holiday set aside for those people.
I don't think the wars in Vietnam or Iraq were very wise, either. But it seems out of place and immature to sound that drumbeat on this holiday, like an atheist who feels compelled to demonstrate outside of churches on Christmas.