The show contradicts your point about speech only being used to lure humans when they speak to each other in private, discussing things such as parents.
The demons came to a town disguised as a peace envoy, a pretend diplomatic mission to disable a magic barrier. This absolutly goes beyond just immitating speech.
Yeah they even showed a flashback to show how little they care about life. They only use speech as a means to an end for killing humans.
The show contradicts your point about speech only being used to lure humans when they speak to each other in private, discussing things such as parents.
spoiler
The demons came to a town disguised as a peace envoy, a pretend diplomatic mission to disable a magic barrier. This absolutly goes beyond just immitating speech.
Exactly.