I grew up listening to the radio. Commercial radio stations would play a small handful of songs again and again. They were paid to do that. The effect was that listeners would either end up loving or hating the song(s) purely through repetition.
Normalizing hate works in a similar way. When a message is repeated frequently and simultaneously, listeners will either block it out or it will become an ear worm, something they repeat in their heads solely out of learned habit.

A 'friend' on Facebook shared a comment about the look on the face of a teenage boy who we're told was mocking a Native American elder on the steps of the Lincoln Memorial this week. The FB friend said that anyone who has ever been an "other" and been bullied or harassed for it, would recognize the malice in the eyes of that teenager. And it's true.

I remember the look of confusion, frustration, and also anger in the eyes of people who knew they hated me but didn't know why. When in groups, these confused strangers can be really scary.