The basic idea is that if the USA does anything that falls short of perfection, then it might as well do nothing at all. (This does not apply to the Palestinians, of course. They are free to commit war crimes, as attacks directed against civilians are, but are immune from criticism by the Left.)

By this standard, we should not have fought WW2 because we lost 450,000 men and women in doing so. We must fight only wars without either American or civilian casualties. This means that we can never fight at all. Which implies that the Department of Defense is a useless appendage, and should be amputated, the money saved going into massive welfare projects.

I recall (but I might be wrong) that Al Gore said something like "If I were President, I could not order the armed forces to carry out any actions that might result in innocent lives being lost." (This is NOT a direct quote, but only a foggy recollection.)

If you are not ready, willing, and able to command the armed forces of the USA, then you have absolutely no reason for attempting to become the President thereof.

Perfectionism is a curse. Rational persons understand the notion of compromise, the idea of doing the best that we can. There is no excuse for failure to do our best, but that does not mean that we need to be perfect.