I would argue that it was actually William Alexander Smith
B-P was a vice president of the BB before he founded the scouts. If B-P wanted a militaristic youth organisation then he was already a member of one at that point, but he decided to form his own organisation instead. Note that @Enkita’s earlier comment
is entirely accurate.
I still say that the early Scouts were hippies in comparison to the BB, and the gap has only widened in the UK. The BB still has militaristic ranks (and, yes, they are important in the organisation).