I had similar with "All things bright and beautiful" a hymn that was a favourite with small children in English schools. Hymn of Christendom? Big No-no.
However I reasoned that "If God chose His Organization in 1919 (I know ... I know ...) then stuff written prior must be OK especially if there is nothing unscriptural about the words."
Now no-one started singing non-jw hymns around me but it does put another perspective on the Hallelujah chorus doesn't it?