FWIW seems to be about some particular protest, but I don't know which one. Clearly (and this is a theme of many songs from the 1960s) it has a very strong current of "hey nobody is listening to us or taking us seriously" -- where "we" is "the young generation" or your term for the war-protest generation (people in their late teens or twenties during the late 60s/early 70s).
Young people speaking their minds
Gettin' so much resistance from behind
There are a lot of songs with this frustration of not being taken seriously. Some include:
Enter the Young (The Association)
The Times They Are A-Changin' (Bob Dylan)
(Hey Hey) We're the Monkees (the Monkees)
Randy Scouse Git (the Monkees)
most of the songs from Hair (Ragni/Rado/McTheotherguy)
What I find interesting is I can't think of any Beatles songs to add to this list! There are anti-war songs (Happy Christmas/War is Over, Give Peace a Chance) but no "the voice of the young is not being heard" ones come to mind. Could just be because I'm tired and it's late.