It's the Song About the Love Between My Brothers and My Sisters

"During their recent 'Summer for Marriage' tour the National Organization for Marriage played a Peter, Paul & Mary recording of Woody Guthrie’s “This Land Is Your Land” during their rallies, without the permission of the artists.

"Kathleen Perrin, a participant on the Courage Campaign's Prop8TrialTracker.com, contacted Peter Yarrow and told him. Yarrow called the use of the song by NOM “heartbreaking” and said that he would be contacting NOM asking them to stop ... "   [READ MORE]

Thanks to qe2 for pointing this out!