There is ample photographic evidence that Blacks participated in the War on both sides, some willingly, some not.
It is not a question of if, it is a question of how many.
Same with the Irish, they fought on both sides and for a variety of reasons, most of which had nothing to do with slavery.
Then why not leave it at that, the truth? Why embellish it with nonsense about whole black confederate regiments and lies about Grant owning slaves until the ratification of the 13th Amendment? Aren't there enough facts about the confederate side to present without resorting to fabrications?