They did not reveal the purpose of the docudrama precisely because the Temple of Darwin cult has something to hide. It’s kind of like investigative journalists or law enforcement officers who use hidden cameras to expose a crooked politician, an evo-cult masquerading as science, etc. I have no problem with this whatsoever.
And did they find out anything damning through their deception? In the CMI article, the movie's director goes to great lengths to demonstrate that the scientists' quotes are accurate. As far as I can tell, they didn't reveal any deep dark secrets. Besides, secrets about what? Darwin's life and thinking? That's in his books!
Face it, they deceived when the didn't have to. Maybe if creationist filmmakers didn't already have a pattern of deception, scientists would trust them more.
You make it more difficult to distinguish creationists from Islamists. You can't accept science in your churches/maosques, yet you want to assert your radical religion on children in public schools.