TV's "Gail and Dale" (Gail Farrell and Dick Dale) sing a notorious "pot" song - "One Toke Over The Line" on the otherwise squeaky-clean Lawrence Welk Show.
I seriously doubt anyone in this clip has a clue what the song is about. (This is the same Lawrence Welk who once fired "champagne lady" Alice Lon for showing too much knee on camera.) It has the words "Sweet Jesus..." in it, so that's probably why Welk assumed it to be a "modern spiritual".
I have a feeling somebody from the band suggested it as a prank, and it somehow made it all the way to broadcast.