He did IOTL and he didn't punish anybody for the massacre in the Battle of the Crater, the largest massacre of USCT in the war, and refused to trade
black POWs in Union Blue for white Confederate POWs. Lee the Marble Man should be dynamited into powder.
The thing I really don't get about that one (bolded) is that a nonideologue would have done it and treated the consequences as less undesirable than the consequences of standing firm on "no exchange".
Or at the very least, pressed (hard) on Congress to make that official.
Lee, to his shame, did neither.
And I'm looking at this purely in terms of Lee not being as reasonable-minded as he's said to be. Screw human concerns, Lee should have encouraged taking prisoners specifically to exchange his own captured men.
But noooooo. Bobby had to cling to all that made the planter class an abomination second only to the Junkers.