I find it kind of laughable, actually. I mean, obviously, I don't know what happened there, but it is immaterial. Do What Thou Wilt is all about personal freedoms, and quitting the addiction of slavery. Whether Crowley was insane or lying or not is beside the point. Would any book discrediting him cause anyone to think "Wow, it's all a lie! Personal choice and freedom must be
bad things!"? I sincerely hope not, and if so, it does come from the same grasping at straws Thelema seeks to do away with.
The notion that removing the head of a pyramid destroys all of it is... such Osirian-Age thinking and bears little upon the ideas put forth. It is amusing in its own way, but ultimately childish. This quote by Crowley from De Lege Libellum says it all succinctly:
Aleister Crowley said:
Let this then be of great comfort to you all, that if I be so imperfect–and for very shame I have not emphasized that imperfection–if I, the chosen one, still fail, then how easy for yourselves to surpass me! Or, should you only equal me, then even so how great attainment should be yours!
Be of good cheer, therefore, since both my failure and my success are arguments of courage for yourselves.
And there you have it. In contrast to the prophets of the Dying Gods, Crowley freely admits his successes and failures merely mean we can all do better.