If you are looking for a yes/no answer then it has to be yes however the reality is very much more grey.
I am a Jehovah's Witness, at least nominally. Do I consider myself dangerous? Not at all. Having said that I am still extricating myself from the religion and therefore am still exposing my family, including children, to the teachings of the WTBTS. I guess I could be considered dangerous by some for doing that.
Do I consider any of the people I know in the WTS as dangerous? No. They are generally pretty decent people, with decent lives and are far less likely to commit acts of violence or abuse against me or my family than some of strangers that live in my vacinity. Would they shun me if I was disfellowshipped? Would they support me in refusing a blood transfusion for my child (not that I would of course)? Would they watch me suffer if they thought I was an aposate? In the majority, yes. I guess that makes them dangerous.
In most aspects of their day to day lives Witnesses are no more and, in many ways, significantly less dangerous than much of the population. It's when push comes to shove on matters such as blood, shunning, education, financial independance, charity and so on that their unwavering adherence to WTS dogma becomes dangerous. Their refusal to think for themselves pushes them into life changing decisions that often affect entire families, including those too young to make their own choice. They act without reason, in blind faith. That is dangerous and although the outcome may not be life threatening (although it can be) it can still be life changing for the worse.
The worst of this however, when the decisions are life threatening or make large, negative and material differences to the lives of others that can last for years, destroying people in the process.
