So no school orchestra can play Dvorak's "New World Symphony" (aka 'From the New World') because a theme from it was originally used for the spiritual 'Going Home'? Brian, by your argument, 'From the New World' would be banned. The lyrics aren't sung in Dvorak's interpretation either. I have issue with this decision - not from a religious or constitutional perspective, but from an artistic one.
Virtually all music is influenced by the composer's identity as a person, including their personal history, their views on social issues of the day, their morality and their faith (or lack thereof). When one starts banning a piece of art (in this case, a theme without lyrics) because of its perceived intent, the next logical step is to view the composer in the same light. Next, Dvorak's other works could be judged by the same broad brush that currently paints Nugent or Bono as 'musical extremists'. The art is no longer the topic of judgement, but the composer is.
I find this to be a distressing slippery-slope.
The theme to 'How Great Thou Art' is a traditional Swedish melody. Adding the words was done long after the original melody was composed. I just find it troubling that a melody can be refused because of later additions to it (that aren't being used in the disputed presentation).