I don't doubt the guy that told me this as he is the straightest arrow I have ever known. That different units have different experiences and opinions is possible. Much has to do with the leadership. I know a few Marines who expressed opinions similar to those in the letter, but they are admittedly modern liberals. Most other leathernecks I know are gung ho.
Perhaps your friend elected to associate with some of the exceptions because that is what they are...the exception.
A modern Liberal and a Marine - cognitive dissonance on two feet.