aśraddadhāne vimukhe 'py aśṛṇvati yaś copadeśaḥ śiva-nāmāparādhaḥ [Padma Purāṇa, Brahma-khaṇḍa

It is an offense to preach the glories of the holy name among persons who have no intelligence or no faith in the subject matter. Such people should be given the chance to hear the chanting of the Hare Krsna mantra, but in the beginning they should not be instructed about the glories of the spiritual significance of the holy name. By constant hearing of the holy name, their hearts will be purified, and then they will be able to understand the transcendental position of the holy name.