Of course all lives matter. That much should be self-evident. So what is the problem? Consider this proposition in a setting that is not an emotional one for us: The question of equality for women in a country like Saudi Arabia.
Liberals in this hypothetical country came up with a slogan, "equality for women," which was an embarrassment for the government. The government, in turn, came up with a counterslogan "equality for all."
It was hard to argue against the obvious sense of this new slogan, which neatly sidestepped the fact that it was women, and not men, who were not treated as equals. With this new slogan, the government took the moral high ground, but it also allowed it to continue treating women as second-class citizens.
In the same way, "all lives matter" avoids confronting the reality that in many instances in the past and present, Black lives do not not seem to matter as much as white lives. That justice is not the same for Blacks as it is for whites. It echoes the declaration that, "all men are created equal," which, at the time, specifically excluded Black men.
We need to keep insisting that "Black lives" be made part of "all lives matter." If we continue to do so, hopefully a time might be reached when we can proudly proclaim, "all lives actually do matter."