This guy is full of nonsense. Not only does he misinterpret Hindu scriptures by saying things like Kalki is Muhammad, deity worship is non-Vedic, Vishnu means "the protector" etc, but he even makes up stories to make his point. In a discussion about ISKCON, Naik claims to have gone to ISKCON Kolkata or something and he said that he had a debate with one of the highest gurus there. Obviously in the debate Naik told the ISKCON guru that Gita is a Smriti and that they are disobeying the Vedas by doing deity worship etc. The funny thing is that apparently, the guru was reported to have said that deity worship was "for concentration" and that Gita is a secondary text. No Vaishnava would say something like that. However, I actually read an article somewhere where it was stated that the ISKCON Kolkata people (or whichever temple he went to) said that Naik had never actually entered their temple and pretty much made up the entire story to make himself look more credible!
He purposely spreads misinformation to mislead the masses. Not to mention that his talks are full of rich Saudis and Muslims in general so there is hardly anyone who poses a great challenge to him. He still has not replied to Mahendra Arya Pal as the latter invited Naik to a debate, and I'm pretty sure he knows he will lose (Arya Pal was a former Muslim who became a Hindu. Unlike many Hindus, he actually knows Arabic and understands the Koran.)!