Calling people rats is othering. It’s dehumanizing. If you can’t figure out it’s the same thing that 1930s Germany did to lead to eventually what it lead to, I don’t know what to say, time for a refreshing course on history and propaganda.
Actual rats. Not humans. That’s the tactic. Make sure people don’t see the group you attack as human so that whatever you do to them is accepted by the general populace.