Looks like you're not above creating myths and strawmen of your own. Look around the Internet and you'll find claims of thousands, tens of thousands of Black Confederates. You'll find a few such claims on this very thread and on other FR Civil War threads. If you said that those supposed Black Confederates were slaves forced to dig ditches and build bridges or slaves and servants who occasionally picked up a gun to defend their masters, the posters who make those claims of thousands of Black Confederates would argue that you were wrong.
So what are they implying? That thousands of African-Americans volunteered or wanted to volunteer to serve in the Confederate forces? That they fought in their own Black units or in integrated ones? That seems to be where those who make the exaggerated claims of thousands of Black Confederates are headed. Again, take a look at some of the posts on this very thread.
Now that it's clear that the evidence for these claims is very skimpy, you may see people backing down. But you have to give Gates his due: people who talk about thousands of Black Confederates are talking about more than an occasional manservant or driver or porter who participated in a battle. Sometimes they say that there were many Black or integrated units. Some times they just let people assume it. But there most certainly were claims that "Black Confederates" involved more than a few slaves firing guns in a few battles.
The only myth in the story is the suggestion that slavery was the only or main “cause” for the support of the war.
Now that is a straw man. A main cause or root cause isn't necessarily the "only" cause. The two are very different. It's crystal clear that without slavery we wouldn't have gotten that war at that time with those sides. That doesn't mean that everybody was fighting for or against slavery or that nobody else had any other reason for picking up a gun. It just means that you can't talk about the American Civil War without talking about slavery. Believe me, some people have tried -- some people are still trying -- and they just aren't telling the whole truth.
I don’t “look around the internet” for lunatic assertions, and I don’t know of any significant historian or historical group that claims that there were brigade, division, or corps level black units. But you seem to ignore that even Gates is admitting that “many” black slaves “fought” alongside their masters -note that the words are “many” and “fought.” In fact, given the numbers of men involved in the war and the timespan Gates’ use of “many” could well be a concession that there were several thousand, although, if there were, I am sure that they were scattered among hundreds or thousands of units.
You mention people “backing down” on their claims on this subject. When I first noticed people claiming that some blacks fought on the Confederate side they were met with categorical denials and derision from people like Gates. The point I was making is that Gates is doing a “climb down” from that position and tries to save face by attacking a claim about Confederate units I don’t believe that even the League of the South has made.
It is simply no longer possible to maintain the comic book view of the sides on the conflict found in many textbooks. Both the relationships between the races in the South and the North and the forces that lead to disunion were complex.
“It’s crystal clear that without slavery we wouldn’t have gotten that war at that time with those sides.”
This is pointless. We could as well say that “without the tariff disputes”, or “without the internal improvement disputes”, or “without the disputes over the meaning of federalism”, or “without the Northern invasion of the South”, or “without the disputes over territorial expansion”, etc. you wouldn’t have gotten that war at that time with those sides.
In the beginning, Lincoln and his supporters were willing to throw the slaves to the dogs with the Corwin Amendment, which, had slavery been the main or only issue for the South, would have eliminated any fear any Southerner had about the federal abolition of slavery. Later, Lincoln decided to use a largely meaningless Emancipation Proclamation to frame the war in terms of slavery to keep the French and British from recognizing the Confederacy. By now, I think most people who read in this subject at all know that while Lincoln didn’t like slavery, he also didn’t like blacks. This was also the overwhelming majority view in the North before and after the war.
The “Jaffaite” narrative of Lincoln and the War as a noble fight to free the slaves and vindicate the Declaration is as ahistorical and the Pollard narrative of the stainless “Lost Cause.” For Gates and other race pimps there is a clear political and social pay-off to controlling the War narrative. That some people on FR insist on manichean interpretations, however, strikes me as odd.