As I said below, that someone does not like such groups, should not mean name calling. Whatever they do to their followers remains them and their followers business. If the follower do not like it, then s/he can get away from them. And I think this is the point where such person's right to not be disturbed by such groups starts.
Nevertheless, I think people should be advised to research before they join such groups instead of being advised not to. Doesn't such equate to the Catholic church advising people not to read Da Vinci Code... it made me to read it instead.
I am not interested in Scientology nor in any religious group, but I do not worry about their existence. They will only offend me if they touch me or step on my own toes. My family members go to their different churches or mosques, and it doesn't bother me what they experience there either. The only problem is that kids should be left to grow without these corruptions; of religion or protests. That child must have been encouraged by an adult.