UNTRUE.
Black Confederate military units, both as freemen and slaves, fought federal troops. Louisiana free blacks gave their reason for fighting in a letter written to New Orleans' Daily Delta: "The free colored population love their home, their property, their own slaves and recognize no other country than Louisiana, and are ready to shed their blood for her defense. They have no sympathy for Abolitionism; no love for the North, but they have plenty for Louisiana. They will fight for her in 1861 as they fought in 1814-15."
As to bravery, one black scolded the commanding general of the state militia, saying, "Pardon me, general, but the only cowardly blood we have got in our veins is the white blood."
Here's another one:
Gen. Nathan Bedford Forrest had slaves and freemen serving in units under his command. After the war, Forrest said of the black men who served under him, "These boys stayed with me.. - and better Confederates did not live." Articles in "Black Southerners in Gray," edited by Richard Rollins, gives numerous accounts of blacks serving as fighting men or servants in every battle from Gettysburg to Vicksburg.
The Louisiana Native Guards again? That doesn't exactly weigh favorably on your side, since they were disbanded after a couple of parades and never saw action as Confederates, but were reorganized by Benjamin Butler and did see action as Union troops.