The idea that Blacks have suffered more is taken for granted here and it actually undermines the argument. Since this makes the case that "injustice anywhere is a threat to justice everywhere," then you can't hierarchize suffering in order to clarify why it is wrong to divide one's racism into categories. The system of white supremacy is predicated upon the idea that one could divide identities and that it would be okay to oppress one group but not another. Blacks have endured a different kind of oppression here in the US than Asians. The particularities of Asian oppression are different the world over. That doesn't mean more or less, but it does mean different outcomes, different results. I'd encourage you to take a page from the Combahee River Collective, and intone that "none of us are free until we are all free."