Because BLM was not founded as a black supremacy group.  They do not believe that they are a superior race, and there has never been any war where black people were trying to take over the world to reflect their image.  Equating BLM to White Nationalists is one of the dumbest things you could do, because by doing so, you are suggesting that the only thing White Nationalists want is equal treatment.  Which is not the case.  White Nationalists believe they are superior and that all other races and religions are inferior and should be eliminated.  In no way, does BLM or even AntiFa represent anywhere close to those views - and in fact, both are specificially against those views.