For war and protest music I think "Fortunate Son" by Creedence Clearwater Revival is probably one of the more popular songs of the time period. Most people, even my girlfriend who doesn't listen to it like I do recognizes this song. It's been in almost every Vietnam movie ever made (or so it would seem) and has a lot of meaning behind it.
While this is a classic rock song, I don't think it has a lot of innuendo per say, the silver spoon in hand is a well known saying of the world and a lot of people used it in the time period that this song was written. This song is about the war and people in it. John Fogarty is the lead singer of the band, and in the song he says "Some folks are born, silver spoon in hand, Lord don't they help themselves." This is talking about the little rich kids that are born with money and get everything handed to them, everything they want. Then he talks about the "Tax Man" coming to the door and the house looks like a "rummage sale" so these rich kids grow up and then they don't pay their taxes, which comes back to them later on. When he refers to not being a "Fortunate Son" he's talking about politician's sons who don't have to go the war because of their father's power. They don't have the elitist government behind them to keep them out of the armed forces while the rest of us normal people are subject to the draft that was going on at the time. He also talks about asking them "How much should we give?" and they just say "more more more." So when you ask the government how much we're supposed to give to help the war effort they basically say that they want and unlimited about of donation. I think this song was one of the more influential songs of the time period, and I think that this is evident in the length of time that this song has been prominent. Other than in the classic rock stations, you can hear this song all over the place, and it's not just limited to Vietnam movies.