Therefore logic is useless against cults. And not all groups are the same. The yeshiva Shar Yashuv that I went to had some things that one might considered sort of cultish but it was in fact a great yeshiva because it was devoted to straight Torah.
You could see this in the great yeshiva Chaim Berlin also. Still to attain the degree of excellence that these places strive for in Torah, a certain amount of discipline is necessary.
To some degree what I think about cults is simple: to learn about them. Information provides a great perspective. It might not take one out of the cult he or she is in at the time but it provides a way of limiting the bad effects. However there is only so much of this kind of thing I can stand reading. Still for myself it was helpful to do research into the problems. It gave me perceptive on my own set of problems.
Also there is nothing quite like experience to show you the difference between the public image and the actual reality behind the facade.
The best cure is to make straight yeshivas like the Mir and Shar Yashuv. And if not a full yeshiva then at least to have a local Beit Midrash devoted to straight Torah and Musar that excludes rigorously all cults and any and all books or writings associated with the Jewish cults. To exclude what the Gra excluded.
However I should mention that there is no reason to hate cult members. Rather the best thing is to pray for their good, that they should merit to repent and to be save from all the kelipot that have taken over their mind's and to merit to be true tzadikim and Tzadikot and to merit to all the good in all the world.