Those movies show the ugliness of war. And those dudes riding around on patrols and getting ambushed, hit with IEDs, having squirters take pop shots at them, seeing the sh!t side of war in the local populace-- they don't want to watch movies about that. Those guys want to escape and laugh a little.
FMJ is bifurcated into two parts. The first part where we all laugh at Gunny Sgt and his jokes about private Pyle, Snowball, Joker, Tex etc. And then the real part-- where the soldiers are faced with surviving as human beings, or killing everyone and possibly committing war crimes.
If you think about it-- Marcus Luttrell and his team were sent to an area to simply recon. It was a picture taking assignment. Nothinf more.
"If this ass hole is here, take pictures of him, report back, and we'll send the calvary to get him."
That was it.
And then a goat herder with a couple of teenagers literally walked right up on them. Fresh can tell you better than I about how freaking hard it was to always have a clear field of vision and how something like this can happen.
But they subdued the 3 people and had a tough choice to make. Let them go, and run for it-- or shoot 3 unarmed men and complete their mission. That's a war crime-- shooting 3 unarmed men. That's 20 years in the brig.
Men in Vietnam were put in similar situations and chose the opposite of what Marcus and his boys chose. No active guy going under the wire daily wants to think about that stuff.