Because there is a strong correlation, not a causation, between ethnicity and culture,
and leftists don’t want to address actual cultural problems,
because that would imply some cultures as better than others,
leading to the question “which one is best”,
they will “shut up” the criticism with a dirty accusation of “racism”.
I think it is reverse from what many think. Liberals use and manipulate elements within cultures to keep groups separate. ‘Rap’ or Hip Hop culture for example. When you get down to the bare bones, it is just music, and every music has various fashion and lifestyle elements associated with it. The left however, has used it as a tool of racial segregation by praising being separate and against many of the unifying elements of our nation.
When we address it this way versus the way many on our side do, we possibly can get ahead of this game the left is playing to keep racial divisions alive.