At some point if the student has learned something beneficial, they will increase in awareness and will begin to see flaws and cracks in the teacher's teaching that they did not notice before. This indicates teaching has been accomplished in some way. It may be necessary for the student to then move on to a different teacher who has the ability and appropriateness to teach the next lessons that the student is ready for.
There are teachers who teach to large numbers of people and many of those teachers are not necessarily teaching the whole truth. Now, the ego jumps in here because the ego is fantastic at drawing comparisons, measuring-up who is who and who is saying what and whether said persons are being 'as truthful' as others. It loves to make a competition out of everything.
The are two sides to this. From the student's point of view they will start to compare teachers and find ways that their current teacher is flawed and become disillusioned with this teacher. They are recognizing that the teachings being offered have been outgrown, but they are still expecting that this particular teacher is meant to be the teacher of ALL lessons, and that they're failing to be 100% authentic. This comes about because the student has become attached to the teacher and has set them up with idol worship in some way, which is part of what caused them to come together initially.
The other side is from the teacher's point of view - remembering that as the student progresses they become a teacher also to those who "have less light" - and so the teacher is now aware of the flaws and shortcomings of the message being given by other teachers who seem to be 'behind' them on the path, and begin to downgrade them as inferior students and as being wrong for teaching what they're teaching. This is all ego and is driven by insecurity that their own teaching and learning is incomplete.
Now, what we need to recognize here is this. "Those who are to meet will meet" - ACIM. There are appropriate teachers and appropriate teachings for everyone, based on exactly where they are at, their individual curriculum, what they need to learn and can learn and are open to learning at the time. Everyone is very different and has their own path. There is rarely a single teacher who teaches everything to everyone, because usually the ego is too strong in novice students to accept full exposure to the truth that might come from a 'higher' place. So instead the Holy Spirit works with everyone where they're at and sends them the appropriate lessons and teachers at the right time, to take the next small steps on their path.
Without an ego comparison entering into it, those who are therefore 'teaching less truth' have perhaps volunteered to fulfill the role of building bridges between those who are teaching even less truth and those who are teaching more. Just because these teachers do not have all the answers doesn't mean we have to hold them accountable or find them guilty. They're providing a service. Even Hitler is a teacher. Even Saddam Hussein was a teacher. Even Jack the Ripper was a teacher. For the appropriate students, these people taught what needed to be taught and what could be learned by the appropriate students, who agreed to be exposed to those lessons because they needed to.
So instead of us saying, well, ok Marianne Williamson, Wayne Dyre, Deepak Chopra, Oprah, etc.. instead of saying like they all teach only part of the truth or they're not totally pure or they're guilty for peddling lies - and technically they are not telling the whole truth so that's true - instead of them being guilty for falling short of perfection, recognize instead they are the right teacher for the right students and the people attracted to them will naturally be drawn to do so because thats what those students need, psychologically. They're not ready for a greater truth. They're not willing yet to open up to a greater truth. They need a bridge. They need stepping stones. And therefore these teachers are being really helpful by positioning themselves as the bridges to a higher place.
So what you can take away from this is... recognize that it's okay to like who you like and to learn from who you're learning from and you don't have to listen to certain people if you're not resonating with them. You will naturally flow to the company of the people that you are ready to be receptive to and that you can open up to and learn from, regardless of where those teachings lie in the big picture. Everyone finds their way to God eventually and it doesn't matter that it takes a very long time or that people are 'deceived' temporarily along the way. When students become aware enough in their own true learning they WILL learn to recognize a greater truth and WILL discern and WILL know when there are flaws and WILL move on when they're genuinely ready. So let them have their teachers and their lessons and where they're at. And let yourself have your teachers and your lessons and where you're at.
Do this without trying to force yourself to always be absolutely perfect and whole before you're ready, and without making yourself guilty for liking who you like or not liking who you don't - that's your guidance system - your program for today's performance. Trust where you are at. You are in the right place at the right time doing the right thing with the right people. You are on the right path. You have the right teachers, unless you're transitioning to a new one which in itself is also right. And so is everyone else. The freedom to let others be where they are at without pressure to be where they're not, gives that same freedom to you.