I have no problem with Dylan recycling melodies, but why claim words and music by Bob Dylan when he clearly didn't compose a lot of them?

And you can ask the same question of Woody Guthrie, A.P. Carter, Robert Johnson, Bill Monroe, Tom Paxton, Richard Farina, Pete Seeger, Mississippi John Hurt, Pete Seeger and so many others.

Pete Seeger actually suggests writing songs to older melodies. He calls it part of the "folk process."