But, as per your own source, this unit was not involved in combat. It was not even allowed to escort POWs. When the Confederate Army needed more white officers, it poached them from the 1st Louisiana Native Guard and that unit was forced to disband. This sequence of events does not support the claim that “thousands of African Americans fought for the South during the Civil War.” If we are to draw any lesson from the 1st Louisiana Native Guard, it might be that, “thousands of American Americans purchased their own weapons and uniforms and offered their services to the South; they were refused, and later disbanded, so most of them put down their arms and the rest joined the Union.”
A textbook claimed that some blacks served in the Confederate Army. This upset some people who found the idea to be politicaly incorrect.
Did some blacks serve in the CSA? Yes they did.
Did they do so in the "tens of thousands"? No. But I haven't seen anyone make that claim here.
Did they serve in the front lines and win many battles for the South? Not that I know of, but I haven't seen anyone make that claim either.
There were free blacks in the South, and some of them enlisted. This is known to be true. Whether they drove mules, served as cooks, or guarded wagon trains really doesn't matter. All soldiers deserve recognition.