Lee believed slavery was a necessary evil that God would eventually remove in some far future time. Lee inherited slaves from his mother before he was married. The slaves inherited from George Custis technically belonged to Mary Custis Lee, but Robert E Lee was the executor, and worked the slaves harder than Custis had. Lee was legally required to free the Custis slaves no later than five years from George Custis' death, but Lee petitioned the courts for an extension, which the courts denied. Lee's Army of Northern Virginia enslaved free blacks in their invasions of Maryland and Pennsylvania, but Lee did nothing to punished those involved. Lee's army massacred surrendering black troops at the Crater, but Lee did nothing to punish any of them.
Nathan Bedford Forrest was more of an abolitionist than Robert E Lee.