So you are saying that if you want to shoot a film about the army killing and raping people the Pentagon won't help you out by letting you borrow some tanks for some of the scenes? You could still use replicas, CGI, or even borrow a privately owned tank so I don't see this issue.
The reason you see a positive portrayal of the US soldier in movies is because a large percentage of the audience either is or if friends with someone who is a soldier. So unless you movie is explicitly about evil US soldiers there is no profit to be had in portraying the US army in a negative light.
Sorry, I was not clear. The military uses a light touch to shape perceptions, but the most powerful force is still indirect censorship.
Filmmakers don't offend people without gaining something from it. It's not just a question of the military + audience but also producers and actors etc. Also, sound effects people don't bother using actual hoof beats when people are so used to hearing cocoanuts and writers / producers don't challenge perceptions unless that's their direct goal.
PS: The DoD does not try and get people to think that most US soldiers are Captain America wannabes. The goal is closer to: "Well trained, Deadly, Loyal, Young, Americans, that need all the support they can get." For various reasons they would rather be seen as crazy than infective.
The reason you see a positive portrayal of the US soldier in movies is because a large percentage of the audience either is or if friends with someone who is a soldier. So unless you movie is explicitly about evil US soldiers there is no profit to be had in portraying the US army in a negative light.