I have been to the Viet Nam Memorial. And yes it does make me sad. But not like the sad I felt when reading your post. It didn't have anything to do with the soldiers we have lost in Iraq or the thousands that have been wounded.
I am being truthful with myself. When a young kid raises his hand he takes an oath of office to protect our country. His/her oath does not specify which countries he will or will not deploy to. Don't be so literal. It is normally the POTUS that gets us into any conflict with the help of our political appointees.
I don't believe we should be in Iraq and never have. And if you spent any time in the Pentagon over the last 6/7 years and you see all the wounded from Walter Reed being pushed through the halls of the Pentagon and you would be sad also. Maybe sad is not the correct word to use, it is more like it makes one feel kind of sick. These young kids are not being pushed for us to see. This is an outing for them. Most are so excited to be in the "Pentagon", you should see their faces.
And yes, I had personal friends that died in the attack on the Pentagon. I could have had more. I worked on a daily basis with a group of about 30 guys (military and civilian) that had just moved out a week before (due to renovations) from the main section that was hit.