They are anti-black, but that replacement theory is about immigrants, specifically Hispanics. That guy is a degenerate, and unhinged people are the only ones who are going to not have empathy for the people in Texas or be appalled by those unspeakable acts. That being stated, the anti-immigration stance has nothing to do with Black americans. The only reason you are even attempting to bring up black people is because you are aware that many Hispanics, particularly Mexicans, have actively supported white supremacy (the overwhelming majority put that they are white on questionnaires, whether that is how white people view Hispanics is really something else altogether) and are not going to have any allies if apathy is what black people exhibit to white nationalist arguments about Hispanics.