Those who lead by example – or walk ones talk – are easier to believe, even if they do not meet our expectations all the time. By advising what they are doing (or trying to do) they have a credibility, and greater probability of being able to help us reach where they are on the path. This does not mean they are the correct teacher for everyone, only that they have an ability to help.
Belief should not be based upon reports, stories, traditions, scripture, logical conjecture, inference, analogies, agreement through pondering views, popularity, or the thought, 'This contemplative is our teacher, rather based on where what they say aims and how they live up to it!
At the end of the day I may be right, I may be wrong, but I share this hoping I am one, the other, both, or neither.