Neutral ground is that injustice is wrong, no matter who it happens to. It's wrong when it happens to blacks, it's wrong when it happens to Asians, it's wrong when it happens to Hispanics, and it's wrong when it happens to whites. That's neutral.

From there, you look around and you see that blacks and Hispanics seem to have injustice happening to them in ways that don't often happen to whites. (Not sure about Asians; but my perception is that they may experience injustice, but less of it than blacks.) And then, coming from a position that all injustice matters, when you seen injustice happening more to specific groups, you say "That injustice matters." Not that it's the only injustice that matters, or that other injustice doesn't, but that specific injustice seems to happen a lot, and it's not OK. We need to do something about it.

I see your example of a neutral stance, and it’s true, and racially neutral. It’s also not relevant to the conversation around BLM, which focuses on anti-black injustice. I take issue with that ALM is used to subvert BLM; why else would the phrase exist and popularize at this time and context? Therefore, ALM is not an assertion of the neutral stance you propose, but instead a rejection of the reality or importance of race-specific injustice.

"The lives of people to whom injustice happens due to extra-judicial murders by the police, who are predominantly black matter and should be considered" doesn't exactly roll off the tongue.

In contrast "Black Lives Matter" describes the issue exactly, succinctly and pithily. As a bonus it outs the people who want to remain willfully ignorant about it.