Ruiz is rationalizing his decision to be part of this movie. He probably, truly, does not want to betray the Marine Corps, but the seduction of being in this movie was too great for him to resist. So, he is spinning things in a way that allows him to believe that this propaganda film does not betray the Corps. It does, however, and one day Ruiz will realize that.
That is one superb analysis. Ruiz is 22 years old. He is in for one major rude awakening and a lifetime of self-loathing. I wish it weren't true because any vet deserves some respect. But Ruiz will end up in a hell of his own making (with Leftwing nuts like the filmmaker as his enabler).