As my colleague Jason Riley noted in a column last year, the high abortion rate among African-American women is something people don’t talk about in polite society. Just one of the grim statistics Mr. Riley noted: In New York City, more black pregnancies end in abortion than in live birth. This doesn’t mean that Planned Parenthood promotes abortion so America will have fewer black citizens. But it’s undeniable that this is the outcome of what they are doing.

Contrary to Mr. Tribe’s tweet, the real white supremacists understand and celebrate this. On AltRight.com, someone writing under the name Aylmer Fisher warns against “the pro-life temptation,” because abortion helps weed out “the least intelligent and responsible members of society,” who are disproportionately “Black, Hispanic and poor.” Ditto for Richard Spencer, the white nationalist who in May 2017 led protesters carrying torches and shouting “you will not replace us” after the Charlottesville, Va., City Council voted to remove a statue of Robert E. Lee from a downtown park. Unlike pro-lifers, who want to be “radically dysgenic, egalitarian, multi-racial human rights thumpers,” he says, “we want to be eugenic in the deepest sense of the word.”

Against these white nationalists stand the pro-lifers, and not just on behalf of African-American babies. They also speak for the unborn child with Down syndrome, for the child conceived in rape or incest, for the unplanned pregnancy that will undeniably crimp any career plans a mother might have if she carries the baby to term. These are all hard cases, and the clarity of the pro-life proposition—the insistence that each of these lives is no less precious than any other human life—can make for a difficult political sell.