Well, I can understand why they would like to follow him still if he turned dark!psychic now. I mean, it's possible that the demon horde is still devided. Some might still want to seize the world as an organized army rather than go on a rampage by themselves. They might still want to follow the YED's plan and Sam is the only thing that's left of the YED's plan. So if he turned evil now, he could still unite them and make them strong and invincible again. Maybe that's why some of the demons want to kill him, to make sure that this would never ever happen...