From one of my military guys:

You’ve hit it right for me. Soldiers are surprisingly
sentimental (to those who don’t know us) about
critters and such (8 cats, 3 dogs, 2 horses here).
Even the ones among us who still hunt after a combat
tour (though I admit to knowing few direct-combat
types who are avid hunters after combat tours) have
soft spots for critters.
Then you give us this big ‘ol misunderstood ape, who
is the victim through the whole movie, who *still*
tries to take care of the gurl, and then ya cast us
military guys as the ones who have to take him out.
Fark. Most of us would rather shoot Jack Black’s
character than the ape. We identify with the ape.
Okay, I’m *really* done projecting now. But put me
among the ones who isn’t going, *precisely* because I
know the end. I knew the end for Blackhawk Down, too,
of course, but that’s… different. It’s my money, I
don’t have to be rational!
Cheers,
Yer Military Guy.