Some people in the academic community have been given lavish support to protect cults.[The very people that write reports on cults are getting lavish gifts from those cults. No wonder they give them clean bill of health.] The attitude is embedded deeply in sociology departments-- to defend religious cults and claim there is no such thing as brain washing in spite of overwhelming evidence to the contrary.
The setting is simple. Control of the young persons' environment by the group under the leadership of the charismatic leader. Once you have those two components in place, brain washing becomes amazingly simple.
That is not to imply all religious interest is due to this, but some of it certainly is. If you can control these factors, you can convince anyone of almost anything, long after the group is gone.
[There is a lot of research that needs to be done here. There is a paper by Benjamin Zablocki that goes into some details, but there is much more insidious history behind it all.]
Still there are legitimate establishments like the authentic Litvak yeshivas which are on the side of good--but they border on cults just by the fact of the cults trying to gain entrance.
All in all I would have to agree with those parents who are wary of all yeshivas unless it is a place that is so well known and established like Ponovitch that there is no doubts about it.
The trouble seems to be that you can take even a good set of doctrines that point people in a moral and good direction and still easily turn it into a cult by these two simple mechanisms--a) control of environment b) charismatic leader. Thus even Torah can be turned into a cult.
The trouble is also that sometimes decent and good groups partake of some of these characteristics. The Marine Corp, or the Shar Yashuv Yeshiva in NY. Still the goal of the group seems to make the whole project worthwhile.
I have thought to mention that Dr. Zimbardo thought the only solution to the problem of cults is to have a healthy society in which the temptation of cults does not exist.