Do you actually think the men who made Pickett’s charge were thinking about slavery in that hell? Grand causes are invented by politicians and historians after the fact, and then used and abused by others to push their agendas. Common soldiers have more pressing concerns.
My father in law was a German soldier, wounded and captured by the Americans when he was eighteen. He was no Nazi, just a foot soldier. He returned home to a country of rubble. I once asked him if he didn’t hate those who destroyed his country. He said no, Wir waren alle Soldaten. I guess you have to have seen war to understand that simple statement.