Imagine trying to prove to someone that firmly believes in leprechauns that they simply don't exist. Where do you start?
An excellent saying I have heard is "Extraordinary claims require extraordinary evidence."
So the burden isn't on anyone to prove it isn't God's organization, but merely to debunk the notion that there is anything particularly extraordinary about it.
So all you WTS apologists who keep saying, "hey, they're only human." You are absolutely right! They're human guided too, and nothing more.