But I mean all lives do matter. I see people get offended by that statement. All Lives Matter includes blacks, hispanics, whites. Everyone.
If this was a question of mathematical logic, you could create a nice Venn diagram and "Black Lives" would be included in "All Lives," which would make "All Lives Matter" inclusive of "Black Lives Matter." But the sociological context is a nation whose founding document used the language "All men are created equal" while simultaneously excluding people with darker skin from that conceptualization of "all."
Given that the United States has yet to grapple with both its past history of race-based slavery, and its current reality of pervasive racial discrimination, many people still hear "all" as implicitly exclusionary --and in fact, many people do use it in that way. While there were initially people who embraced the concept of "all lives matter" in a genuine attempt to be more inclusive, this phrasing now used most often by people whose agenda is to stop the progress towards racial equity represented by the "Black Lives Matter" movement. Its use exploits the positive and inclusive literal meaning of the words as a disguised way of affirming a social context that is tilted sharply against members of a particular identified race.