So I’ve been thinking, if hate is just the great of something you doubt know, does that mean Hate!Sans, when he was possessing regular Sans, was he trying to inflict fear of what the people do not know to the point of rage to gain power? Or nah?

rumours can do a lot of damage to people, grudges start, drama starts. hatred builds up and ignorance of the situation shows, you get the idea. hatred spread around like fog because of mere rumours, misunderstandings, etc.