Scouting for Boys is basically what he started out with. He then lived on to nurture the organization into something else. Other life outlooks than his own, including atheism, was never really problematic. Otherwise it wouldn't have spread to muslims, jews, atheists and so on. All of this matters very little however, as Baden-Powell's ideas aren't gospel. The organization doesn't exist to teach hundred year old ideas about how boys should behave. (It's important to know that the national organizations have a lot of leeway in shaping their own program and the BSA is unique in a number of ways.)