It told him "this is what our religion says we should do" without any kind of weird prompting, role-playing, or persona-shifting beyond using a different language. As a westerner, you may regard athiests with suspicion, or even contempt, but you've at least heard them speak publicly. From a culture where most haven't, hearing an authoritative voice which can perfectly cite support for any point it's making, how could it not have a huge potential for radicalization?