Wigmore says that bringing into court statements made by people not presently in court in order to prove the thing the out of court person stated is true should not be allowed. How do we know that person was telling the truth if we can't hear it from them/cross examine them?
I wouldnt say people acting against racists are even close to as bad as actual racists but I will say that identifying everything and everyone based on their race, and assuming anyone who is white is racist etc. is ridiculous. And that will only sow more hate and discord in this country.