I think a kind of shock treatment is needed. A kind of wake up call. People are for good reason reluctant to leave something they got benefit out of,- even when they start to see problems.
[A good hint is when most people that know the subject fairly think the group you are involved with is a fridge nut house group. Maybe then it is time to pack your bags.]
My suggestion is: Even when you know there is a gap between what you know is right and your actions- to still keep on learning Torah and Musar, so that when the wake up call comes, you have the intellectual ability to leave something that you knew all along was not good, and you knew you were just making excuses for it.
So I again am making an argument for learning Torah. This is something I got from Reb Shmuel Berenbaum at the Mir in N.Y. When he was asked about almost any human problems, from all kinds of people, his answer was always to "learn Torah." He felt the Torah had the ability to guide people towards the truth that they needed in their own lives. Just for clarity: The idea was to learn the Old Testament and the two Talmuds. I mean to say his definition of "Torah" was very much like the Rambam's statement "Just like there is no תוספת nor גירעון in the Written Torah, so is there no תוספת nor גירעון in the Oral Law."[You can not add to the Tenach, so you can't add to the traditional books of Oral Law. People can write books to explain the Oral Law, but they do not constitute the Oral Law in themselves. So the only real, authentic Oral Law is the books we received from the Talmud Period. Everything else is commentary which can be wrong.
There might be other examples of groups that have things that are wrong. However an example is the idea of מסית ומדיח that is one who entices others to do idolatry. That is you might have a group which has lots of good advice for you and has helped you and also the leader has done great miracles, but as part of the group there is worship of the leader. We know from the Torah that idolatry is forbidden so when worship of the leader is an essential element of the group then trying to bring others into it has a category of מסית ומדיח and we find the Dark Side often gives people miracles in order to give them the ability to entice others. This is common and also common knowledge.
The fact that lots of people believe in a cult does not provide evidence for truth value. "Some markets work well, but the market for ideas doesn't. Why not? Because ideas have massive externalities. The market for pollution works poorly because strangers bear almost all the cost of your pollution. The market for ideas, similarly, works poorly because strangers bear almost all the cost of your irrationality. The people who pay the price for the lies are not those who control the movement.
Truth doesn't largely win out in a well-functioning market for ideas, because people primarily seek not truth, but comfort and entertainment. Look at the market for religion. No matter what your religious views, it's hard to claim truth prevails, because even the generously-defined market leader has less than half the market. The same goes for political ideas." Brian Caplan