Billy thinks the Tralfamadorians will be freaked out by how much murder there is on Earth.
Billy has been reading a lot of science fiction and thinks aliens will be concerned about Earth's warlike nature and advancing weaponry.
So he asks the Tralfamadorians, using some of his own war experiences, how a planet can live in peace.
The Tralfamadorians clearly think Billy is being stupid.
The Tralfamadorians tell Billy that they know how the Universe is going to end, and it has nothing to do with Earth. A Tralfamadorian experimenting with new fuels will press a button and the Universe will disappear.