Extremism of any sort is usually not good for the mind or soul, if you will.
I am a religious/spiritual person, but the critical thing one must do when dealing with any information or lesson is to contemplate it, extrapolate it, then abstract it. In short, always ask questions. Does someone who's being "indoctrinated" really know what they believe? This goes for anything, science, religion, etc. Ask questions. Know and understand what you believe and why.
I've never seen this work, and I've never thought it sounded like an appealing watch. However, "documentaries" like this will typically be biased towards the viewpoint of the filmmaker. And if the filmmaker wants you to see something which will try to make you change your mind to suit his or her viewpoint, he's/she's going to show you just that. Makes me think of those silly videos they post on PETA-esque websites... Documentaries aren't necessarily fact. Heck, history isn't always accurate; history changes due to who wins, who's in power, and so on. Look at the sad state of North Korea...