You are right-—I stand corrected on 2000 and 2004, where Bush got 10 and 11.8, but (obviously against a black candidate) McCain got 4 and Minion got 7-—so Trump already equaling Bush’s best with blacks.
OK. I think what shocked Barone is that he expected Black voters (at least in the post-Civil Rights era) to vote more and more like upwardly mobile immigrants as they themselves moved up the socio-economic ladder. But that never happened.
Even in middle-class Black areas, they vote as radically and extremist far-left Democrat as if they’re still living in the slums. Examples of that are PG County in Maryland and (more shockingly) the ever-expanding Atlanta suburbs (DeKalb County and Clayton County).
The latter two places were White suburban Republican counties (which voted for Goldwater in ‘64, DeKalb for Nixon in ‘68 & Clayton for Wallace, both for Nixon in ‘72, Clayton for Reagan in ‘80, Reagan carrying both in ‘84, and Clayton for Bush, Sr. in ‘88), but have become so radicalized and leftist that Clayton is now THE most Democrat county in the entire state of Georgia (in 24 years going from 65% Republican to 85%(!) Democrat and just 14.7% went for Willard in 2012 - McCain got 16.6% in 2008).