Radvaz (4:187): A reason for not punishing preachers who distort the meaning of verses or medrashim is that their mistaken interpretations are the result of their faulty study of the texts. They are no worse than those who err concerning one of the fundamental principles of faith because of their misunderstanding of texts and yet are not considered heretics. For example, we find that the great man Hillel II erred in one of the principles of faith when he said Moshiach was not coming because of the events in the time of Chezkiyahu. Nevertheless, this error did not make him a heretic — Gd forbid. If he had been a heretic, how could the Talmud quote him? It is clear that since his improper statement was the result of sincere study, it was considered as inadvertent and thus he was not a heretic.