Then stop promoting things that encourage a 'my country vs. your country' attitude. Not that I believe for a second liberals want unity. They thrive on disunity. That's one way that you overthrow a given society, and an old way at that. Setting the population against itself is a time honored way of seizing a control of a people group.
Likewise, the liberal mantra of 'stop being divisive and admit you're a racist' doesn't exactly sound unifying for sane people. I doubt it sounds unifying for the Left either. Talking out of all three sides of the mouth isn't foreign to progressive activists. Projection is another arrow in the old leftwing quiver.
So don't be shocked if you hear liberals scream unity while pushing various groups to declare their own America as opposed to others a while saying for the sake of unity everyone who disagrees is a racist. For the liberalism I've grown up with, that's all standard operating procedure And the goal is hell and gone from unity.