If the BoS were portrayed as a professional military organization, respectful to everyone, even-headed, clearly sane, rational and at least open-minded enough to learn from their mistakes, I'd have no problem with them.
As it is, they are inescapably portrayed as amateurish, arrogant, hot-headed, megalomaniac, irrational, dogmatic, prigs who the SS can easily decimate if they choose and who cannot achieve anything of note in the Commonwealth without the help of the SS.
WHY!? Do they just fly around taking potshots at baddies? Why don't they actually hold ground? As you play more, if the BoS was intended to be a potent force: a. you would note that vertibirds no longer blew up regularly; b. you would notice more and more areas controlled by BoS, including checkpoints; and c. you would see the BoS interacting with traders, and other NPCs establishing relationships, perhaps even honing in on YOUR allied settlements.
Perhaps it has more to do with the overall design of the game world in which the SS is inevitably going to wind up either dead, or the hero of everything. But in any event, I cannot accept them getting into firefights and taking 50% casualties (including having incredibly valuable vertibirds downed by the dozens) as anything except a clear indication that they are clowns, and arrogant, impolite clowns on top of that.
So evidence points to Maxson being a courageous and capable warrior, maybe even an effective field commander. As I have pointed out, the organizational aspects of his invasion of the Commonwealth are laughably amateurish and his demeanor when relating to subordinates and strangers alike is more akin to Conan the Barbarian than to even Alexander the Great, much less Abraham Lincoln.
Having killed some stuff and braved death valiantly doesn't make him a great leader. https://en.wikipedia.org/wiki/Dwight_D._Eisenhower#World_War_I before he was appointed as Supreme Commander of Allied Forces.
Seriously you guys who think being a tough guy with a scar on your face and an unswerving dogmatic determination makes a character a "great leader" need to wake up and smell the coffee. Some great leaders and/or great military leaders have shown great courage and capability in combat, some have not. Being a great leader, even a great leader of military operations does not necessitate proven combat ability at all, though it might never hurt.