Shouting Obvious

There is no point in shouting X to the general public unless the shouter assumes that the majority of the public thinks that X is false.
Hence by shouting "BLM" to the general public one shouts that the majority of the general public is so racist that they do not think black lives matter. But that is obviously false.
Hence shouting BLM is knowingly false-accusing the majority of the people.
This political strategy is very potent. Lots of people can be expected to speak-out against the shouting of X. Then those speak-outers can be portraid as not believing in X. This may have 2 effects on the people speaking-out. Both are good for the shouter. 1 : People are afraid to spake-out. 2 : The speak outs that do happen will be used as "proof" of that really some people do not believe X.