Everybody took slaves from prisoners of war in any conflict, not just the Romans. Slavery was ius commune, it had nothing to do with ethnicity and it fit in very different social and anthropological functions across all societies of the period. Everybody stop it with the application of modern, anglocentric concepts to ancient Mediterranean cultures. It was cute when you were just building a whole bunch of anachronistic white marble columns, but that’s as much as I can tolerate.