We must not close our eyes and follow a teacher blindly. The teacher carries a message, but the teacher may not necessarily be enlightened. The teacher is a human being. S/he may still be affected by emotions and will sometimes make mistakes. What we must learn from that teacher is the message, not always the behavior.
It is wiser to separate the teachings from the behavior of the teacher. Then if some action of the teacher should disappoint us, we will not lose interest in the Dharma because of the behavior of one person. Everyone has the same capability as the teacher, the same potential. If we continue to follow the Path, we may go further than some of our teachers.
If we learn that the teacher has behaved in a manner contrary to the Dharma, we should remember that the bond between student and teacher is voluntary, and it is possible that this particular teacher is no longer appropriate for us.
Perhaps this person was never a true teacher, and in that case there is no bond to sever. If a teacher that was formerly qualified should break the Precepts or his/her lineage Vows later, then that action automatically dissolves any bond with the student, and there is no longer a bond to sever.
If we are unsure or uneasy about our teacher’s behaviors, then we should attempt to discuss the issue with the teacher, or with another teacher whom we respect. There may be a misunderstanding and an easy explanation. A refusal to discuss the issue may indicate that the relationship is not worth pursuing. Time and common sense will show the way.
If this is not possible, or if we are still distressed, we can turn to the scriptures of the Dharma for guidance. We should not have blind faith, but also we should not engage in blind criticism. Rather, we must rely on the teachings to evaluate a teacher.