Deciding which teacher to trust can be very difficult at times. I'm quite skeptical, and people really have to win my trust, though sometimes I'll pretend to believe someone and then go check with friends/other teachers/reference material/etc before making up my mind.
It helps to have multiple teachers. Especially as for every one of them, there is at least one detail that I'm fairly convinced they teach incorrectly (usually some of the others support my opinion).
Of course it's worse if a partner is involved, because you might come to different conclusions about who to trust.
Anyway, check with some other authorities. A good teacher can explain the reason behind the way they are trying to teach, in effect, argue for it on its merits. In contrast, someone who simply says "because that's the way it is" either doesn't really know their stuff, or is too arrogant to be your employee. Unless this teacher is so special that they are doing you a favor, you have every right to ask difficult questions. Though it would probably be more usefull to ask them to explain their way than to outright challenge their authority.
Lastly, it is possible to learn from people who have glaring flaws in their dancing - though it can take patience to keep those issues from bothering you, and skill to keep them focused on the things you want to learn from them, rather than the things you've conlcuded they do incorrectly.
