Considering that the slogan being discussed came about as a result of cops shooting unarmed black people and suffering little or no consequence for it, I don't think the phrase can be logically termed 'racist'. If news reports are any indication, the police and the courts in the US seem to have taken the position that black lives don't matter as much as other lives. The slogan is simply a reaction to that.
Boru
Boru
‘I can’t be having with this.’ - Esmeralda Weatherwax