By my observation, every time a demon speaks in the NT (and that's the only place we observe or hear them), it speaks the truth. I'm not aware of any occasion where a demon is deceitful. They always identify Jesus correctly and speak the truth about Him. So saying, Jesus has nothing to gain by getting endorsed by demons. Who wants an endorsement like that? In America that's like having a commercial of the Iranian Ayatollah doing a commercial for your product. Oh, that will sell a lot of merchandise!
![Twisted Evil :twisted:](./images/smilies/icon_twisted.gif)
Nobody would do that. It doesn't enhance Jesus's image and reputation, even though they speak the truth. Nobody wants a commercial from demons.
In addition, Jesus is suppressing the disclosure of His identity. It's very early in His ministry, and He will reveal Himself in His way and His time. This is no way to start out.
> I recently heard someone say do not talk down to an unclean spirit.
This has nothing to do about how we address demons (if we ever address them). Jesus was in a whole different position addressing demons than we are. This text is not meant to be a training session on how we are to exorcize.