Good points, Alex. I agree. Here is a question for you, do you think that the Pharisees of the time of Jesus actually did have, at one point, a true faith, but then lost it? OR, was their order institutional, such that perhaps generations of Pharisees (or other Jewish leaders) were all corrupt before God? I would find it odd if otherwise pious men all went to seed just because of the arrival of Jesus. That would also show me that they had no true faith in the first place.
Nicodemus was a Pharisee and a convert and so was Paul. Both were figures of authority. From these examples alone we know that some Pharisees had the true faith of the Prophets and were prepared to accept Christ.