Lee died shortly after the war which helps. The south needed a scapegoat and Longstreet was it.

historical revisionists

Uh... no? Revisionism just means "critically challenging the mainstream historical narrative." "Lee was actually an evil slaveholder who fought for slavery fuck him" is the revisionist narrative here. The word gets a bad rep because certain people only like to revise narratives about how fascism is bad actually, but revisionism is an important part of studying history, as any historian will tell you.

Lee was revered by both sides at the time.