I'm guessing it received skepticism for the same reasons "The Kingdom" received uneasy approach when it was first released in theaters: A medium attempts to capture the story of a major event during a time where the world is still feeling the effects of that event and the developers release said story to a pansy, hyper-sensitive society that screams "mockery" every time someone tries to convey a powerful story (the Battle of Fallujah) in a compelling and profound way. This is the same vocal minority that would condemn Winnie the Pooh because they thought Eeyore was too depressing.
I cannot speak on behalf of the Marine Corps, but I can say that I know a few of my brothers who would love to support a game like this.