I know I’m late to the party here, but BLM is generally equated with either Marxism or radical socialism. There’s nothing inherently wrong with that, (though I would always question a Marxist with a mansion) and before BLM the Black Panthers were committed socialists doing a lot of good for impoverished communities. But you won’t get anyone even slightly right of centre to endorse anything that has even a hint of left wing politics about it. ‘Black lives matter’ as a conceptual framework for humanitarianism can be agreed in principle. See Simon’s comment, but the conflation of political and philosophical is a non-starter for many right wing or right moderates. You say ‘black lives matter ‘ and they agree, then you say ‘if you think Black Lives Matter you’d vote for XYZ’ and that doesn’t carry through.