I need my NPC to have no dialogue at all, because he turns to whoever he is talking to. This is unwanted. I need him to be mute, so this way, he won't turn anymore by his own. I tried deleting all of his dialogue, but this got rid of every NPCs dialogue too.

The easiest way to make an NPC mute is to create a http://cs.elderscrolls.com/index.php/Race_creation_tutorial. However they will still turn to look at you or other NPC's. I don't know if it's possible to turn off the head tracking. I think that's a global setting that controls the player more than anything else. I'd try searching the CS wiki for head tracking.