They may not change the the minds of "the good and the great" but they do help to establish the fact that we are not alone in objecting to the crap they throw at us.
I'll never forget the affinity I felt with all the other anti-Vietnam protesters in Grosvenor Square when we were telling the occupants of the US embassy what we thought of Napalm and Agent Orange.
They also put on record that the blood of the Vietnamese, Chileans, Nicaraguans, Greeks, Kurds, Haitians, Iraqis - whoever, was on their hands and not ours.
"Disc of sun in the belching smoke,
Blazing huts were the children choke,
Burning flesh and blackened blood,
Charred and blistered like smouldering wood.
Oh brother, did you weep,
Oh brother, can you sleep.

Wall-eyed moon in the wounded night
Touching poisoned fields with blight,
Showing a ditch where a dead girl lies
Courted by ants and hungry flies.

Scream of pain on the morning breeze,
Thunder of bombs in a grove of trees,
Hymn of rubble and powdered stone,
Mangled flesh and twisted bone.

Programmed war, efficiency teams,
Punch-cards fed to thinking machines.
Computered death and the murder plan,
Total destruction of Vietnam.
Oh Brother have you got no shame,
Oh Jesus, they're killing in my name".   

I wish I'd said that - in fact I did, many times.
Jim Carroll