I now believe that absolutely nothing ... will shake Black loyalty to the Democrat party.
There's a tad of a disconnect in what you say, because there were many more black Republicans, percentagewise, back in the 1950s. Nixon got about 30% of the black vote vs. Kennedy in 1960, and probably would have gotten more had candidate Kennedy not helped get Martin Luther King out of jail during the campaign. In fact, King's father was a Republican as was Jackie Robinson.
As an old Abraham Lincoln, Civil War Republican I am well aware of the fact that Blacks used to be Republicans. But that's the point: used to be. They no longer even remember having been Republicans and more to the point, despite their quasi-redneck Fundamentalist worship style (which "multiculturalists" seem to think came from Africa) they have sold out their religious beliefs altogether. The only Black conservatives are middle class or wealthy and aren't particularly religious (Sowell, Williams). The fact is that the Black counterpart of the right wing Bible-banging trailer trash is precisely those poor people who vote as if they had never heard of a G-d at all. And that stinks--the whole situation.