gavra,
I’m not sure what a fraudster has to do with your comment of “Who knows better, the expert who knows the case and has studied the field or the Rav who does not?” If you are moida that a fraud who calls himself a Rabbi is nothing but a faker, then one shouldn’t have such a rasha for a “rabbi” on anything. What does that have to do with expert advice, deferring, and/or the Brooklyn Bridge?
tal’s comment of I think you may be convincing yourself that Rabbanim respond in matters they feel they are unqualified… Rabbanim don’t speak when they are not certain… and the rest of tal’s comment is 100% on the mark.