but groups are made up of individuals, and if we're learned anything recently it's that extremists tend to be attracted to extreme groups. Abortion clinic bombers don't attend UU churches, for example. They seek out groups that reinforce their beliefs and justify any actions as god's will.
Do most Witnesses pose a threat? I don't think so. But I'm sure there are enough individuals in the association that, given immunity from their actions, would gladly go old testament on some people- maybe stopping short of murder but assault is definitely within their comfort zone. I can think of a couple that I attended meetings with as a matter of fact.