In particular, what is the thinking of the church with regards to singing the “Battle Hymn of the Republic” during Mass?
The “Battle Hymn of the Republic” is not a hymn in the liturgical sense. It’s context is the American Civil War–from which it emurged. It has NO place as a substitute for a hymn in the liturgy–even though it was used as a recessional (rather than a more appropriate Eucharistic hymn) on an internationally televised Mass recently.
Fr. Vincent Serpa, O.P.