[RedsBaron]

The Beatles themselves demonstrated that "love was not all you need" in their own lives. Much truer IMO was the song "Without Love" sang, by among others, Elvis Presley: "Without love I am nothing." Love is not ALL you need, but without love, nothing else matters, a truth expressed by Paul in his letters to the Corinthians.
Other lies set to music--how about "Everything Is Beautiful" by Ray Stevens? Many things are beautiful, but some things are terribly ugly.
In "San Quentin," Johnny Cash concluded before an audience of inmates that San Quentin had "done no good." Well, without a doubt there are reforms needed in our prison system, but keeping convicted murderers, rapists and thieves off the streets seems to be "good" to me.
One of the dumber lines ever set to music was in Bruce Springsteen's "No Surrender" when the Boss sings "We learned more from a three minute record baby than we ever learned in school." I sure hope not.