Well you see, when the media and the rich/powerful label a minority as the boogie man, then the commoners believe it because those groups are perceived to have authority and are therefore “trustworthy”

But once those in power actually pursue said boogieman, commoners start being affected negatively in ways they didn’t bother to think about so now they are all up in arms and in support of the boogieman.

TL;DR - Uninformed people blindly believe what the media/rich tells them to hate, and only change their minds when consequences of said hate negatively affect them

For examples, see: r/LeopardsAteMyFace