Girl Scouts IS a corporate entity. They were chartered by the US congress in 1950. They even have a book on what it means to be a
Girl Scout Corporation.
FBB doesn't have many of the traits of a corporation. The have a 501(c)(3) tax exemption status, which can be granted to corporations, but that doesn't define them as a corporation.
"A corporation is a legal entity that is created under the laws of a state designed to establish the entity as a separate legal entity having its own privileges and liabilities distinct from those of its members." FBB does not have that legal status and not created or charted by any government agency.
In order for ACS to allow what FBB wanted, FBB as an entity has to be legally accountable. It's a legal issue, nothing else. I could probably keep saying that until I'm blue in the face and died from asphyxiation (through some divine intervention I spelled that correctly on my first try! o_O) and people who already take FBB's side would never believe it. Probably just because they don't understand (won't bother to take the time to learn about) the differences between corporations and organizations.
It's like minorities almost always seem to claim discrimination when they're denied some official service. It might be discrimination, but there might also be other factors involved.