In the current political context, the term "Black Republican" simply refers to a Republican who is black. But during the civil war era, the term was a slur directed at white Republican politicians, especially to allies of Abraham Lincoln. Since the term seems to be frequently used in recent threads, and also misunderstood, I thought I should give the definition here. This is not my definition alone, but can be found at various locations on the Internet and is well accepted by historians. For example, here is one reference to it:
"From 1854, when the Republican Party was founded, Democrats labeled it adherents "black" Republicans to identify them as proponents of black equality. During the 1860 elections Southern Democrats used the term derisively to press their belief that Abraham Lincoln's victory would incite slave rebellions in the South and lead to widespread miscegenation. The image the term conveyed became more hated in the South during Reconstruction as Radical Republicans forced legislation repugnant to Southerners and installed Northern Republicans or Unionists in the governments of the former Confederate states."
Source: "Historical Times Encyclopedia of the Civil War"
Here is another example of the use of the term "Black Republican":
"Significantly, Floridians could not vote for Republican Abraham Lincoln, who was not on the ballot in any of the Deep South slave states. The hated "Black Republican" Party was believed by most southerners to advocate abolition and black equality, although Lincoln and his party were primarily interested in restricting the
expansion of slavery in the territories."
The above is from this link:
So in conclusion, when I hear anyone use the term "Black Republican" in the context of the civil war, then I think that either they don't know that the term originated as a racially charged slur or less likely that they don't really care.