Penny S wrote: "...In addition, my father became a conscientious objector in WW2, and apparently, so did a considerable number of his fellow BB members, so the military look of the thing was misleading..."
I can't help thinking that this was reaction to the Great War, rather than the effect of the BB.
Somewhere in my collection I have an early BB training manual which includes arms drill (Martiny-Henry carbines), and, IIRC, the Boys Brigade provided a battalion of the KRRC during the Great War.
I think the religious-militarism was genuine, but against the background of the War and with the atmosphere of pacefism in the interwar period such an outlook was doomed.