mhendo said:Actually, it's quite easy for a film (or any other literary or dramatic work) to tell you just as much about the time it was made as about the time period that it covers in its subject matter. Current political and social sensibilities often make their way into films (and novels and plays), even when the films are about totally different subjects or time periods. This can happen in subtle ways, or very obvious ones.
A perfect example, here in the US, is Arthur Miller's play (later made into a film) The Crucible. A story about circumstances surrounding the Salem witch trials of the late 17th century, the play is also a critique of the anti-communist hysteria and McCarthyism of the 1950s. Similarly, last year's Good Night and Good Luck was, in my opinion, as much about contemporary American politics as it was about McCarthyism.
Or you can look at movies about the US Civil War. Birth of a Nation (1915), Gone with the Wind (1939), and Glory (1989) are all, in one way or another, about the war and the politics surrounding it, but they can each also tell us something (quite apart from cinematic issues such as B&W v. colour) about the sensibilities of the times in which they were made. All demonstrate vastly different attitudes towards the institution of slavery, and the role of blacks in American history.
You ask about Platoon. Well, like other Vietnam War movies, made before and since, this film reflects changing attitudes to the war in the United States, and reflects particular ideas about what the war means (or should mean) to the American people. Some Vietnam War films focus on heroic battle scenes, others on the perfidy of the NVA, others on the post-war issue of POWs allegedly still held in camps. Some focus on the impact of the war on returned soldiers and on American society (Deer Hunter, First Blood, Born on the Fourth of July), while others focus on class and authority and danger within the ranks during the war (Platoon, Full Metal Jacket).
All of these films can tell us something about the time they were made, and about the people who made them. In fact, i'd argue that they often tell us more about those things than they do about the war itself.
Wow, that's like crazy !!! I'd never have guessed that, like, art isn't, like, just about the story and stuff!!! You have well and truly opened my eyes !!

Chill, just 'cos your primer was so basic it assumed anyone who approached art, in whatever medium and intellectual context, is infinitely stupid and unable to place it in its historical context, doesn't mean you have to get offensive. 
