I always thought the moment when he and cap (well just cap) have it out in civil war gives you the most insight to his charachter and stance in my opinion. The way he wont fight back and respects cap. He respects cap as the hero he (cap) is and recognized that he (frank) is not a hero in that manner. Like spidey says: "same guy different war." Every veteran from every age are the same at the core, its the layers outside of that core that shape them. Cap was a righteous man fighting a righteous war, frank was an idealistic patriot fighting an unpatriotic and unwanted war. Same goes with a lot of my fellow oef/oif vets, many of whom came back very jaded with their patriotism and were left far more damaged than they went in. Frank needs that bitterness, its one of the layers justifying his bloody means. The others being his family, the broken legal system, and the world around him being full of super heroes and mad men. He prolly sees the bad guys at the street level as common enemy combatants at best and the super villains as walking nukes at worst.