This Zakir Naik guy, unfortunately, looks like a great example of how effective confidence is when speaking to an uninformed audience. If your audience doesn’t have their own expertise to weigh your words against, they will judge you on your confidence alone. I hadn’t heard of him before, but his Wikipedia page suggests that he’s a fairly popular Muslim televangelist. Being an overconfident blowhard is an effective way of sounding like an expert when you are talking to non-experts. (This is also reason number 4 of ∞ why “doing your own research” is often a bad idea.)