There's a difference between excusing and forgiving.
Thinking of Byrd's early racist ties -His KKK participation isn't excuseable, the philospophy and actions of the KKK offend every moral principle I grew up with. Up here we had not lost the war and seen our subjects and servants raised up to be our equals at its end. In that war of cultures, our side won, and imposed ours over theirs, and afterward a cultural guerilla resistance spread through southern culture in response. That was the whole obsession with states rights, and Jim Crow. Where black people had been objects of condescension as owned servants, freed they became symbols of the south's defeat, and objects of hatred. The Civil Rights Act was maybe the last battle of the Civil War. And the south rose up to fight it. Lost again.
George Wallace was famously still fighting the battle when he fought against school and lunch counter integration. He's now famous for switching sides and embracing the change he fought against. Not that it matters to anyone, but I've forgiven George Wallace. And Robert Byrd too, for the same reason. In Byrd's case, I wonder how many there are who will never forgive him for switching sides.