Yes, most, if not all, teachers are imperfect. Even the Buddha made mistakes.
It is great to feel gratitude to the teacher who has brought the Dhamma into ones life and hard to see his faults sometimes. But if the teacher's intentions are basically good and there is some Right View, she/he can be a wonderful blessing inspite of the imperfections, I feel.
I am sorry if this is
here, I don't know the teacher under discussion and I agree that "mine is the only way" rings alarm bells, but I hesitate to criticize.
As an aside anecdote, a fellow Buddhist Religious Ed teacher at the school I do this, is a student of a student of Geshe Micheal Roach, a Tibetan teacher who had gone off the rails some years ago. I actually had read a fair bit about it, but I never mentioned anything to her - it's all widely available and I am no judge of anyone else's practice. Instead a positive support is more useful I think...