I think it's very difficult, which is why no one wants to discuss it.
It's so important to check out the credentials of anyone you're going to create a Guru/student relationship, although there's no guarantee that such problems will not arise later on.
I think you've got to look logically at the reasons why you should believe or disbelieve something, and also the effects of the view that someone is espousing. The worst situation is to believe someone just because of their title or credentials. I think it's possible to deal with conflicting advice by thinking "well, I can't see any logical reason why they would assert that view and it doesn't fit with my karma at the moment, so, I will continue to follow and respect this Guru in every other way and sincerely practise their teachings and then, in my heart, ask for forgiveness because I am unable to accept or practise their advice on that particular issue at the moment"
What else is there to do? It must be a very painful situation to be in.