"I am going to get to some very important points that actually prove that black lives do matter and we have to take action together." - Clinton 10/13/15The genius of "Black Lives Matter", as a political slogan, relates to what psychologists would call its underdetermination. Taken literally, it's not actually making any kind of inflammatory or controversial argument - but this is because modern political discourse has emptied antiracism of all meaning, so that one can plead "of course black lives matter" even as one supports police brutality, austerity, employment discrimination, and all of the other afflications that plague black Americans. It is this very emptyness that makes #BLM such a potent Rorscharch. The subtext people read into it has nothing to do with some kind of real latent meaning to the phrase - it depends entirely on their relationship with the speaker. When a racist hears a black American use the phrase amid an aggressive demand and assertion of her rights, of course he is going to read all kinds of bizarre subtext into it.
That's why I find it so nuts that Clinton's response to hearing "black lives matter" is to set out to prove it - as if black Americans are asking for her validation, or as if racists are simply waiting for a sufficiently persuasive counterargument. Black Americans are not asserting that "black lives matter" as the conclusion of some debatable argument, to be established with clever reasoning and evidence; it is the premise of an argument that is meant to compel conclusions, in particular "police brutality and systematic racism in our criminal justice system needs to stop."
Clinton may be intending to signal solidarity, but what her phrasing reveals, ironically, is that she actually thinks of "black lives matter" as a debateable assertion. She seems awful proud of coming to the right conclusion here, but it strikes me as damning with faint praise to applaud her for endorsing as "proven" such an uncontroversial premise about the value and dignity of human beings. That, unfortunately, is where her liberalism is likely to position us for the next four to eight years: arguing that black lives matter and that we should take action together instead of actually taking action.