It works the further out a historical event goes. US slavery is still very recent compared to Roman slavery. Once 1000 years has passed from the US slavery, historical takes will probably be different from what we have now.
I'm more advising caution due to my background as an exmormon. "Product of their time" is used frequently by mormon apologists to excuse the racist or predatory behaviors of the founders of the religion. I also see it used for excusing the actions of the founding fathers or confederate generals.
When I see someone say "we can't judge the romans for their actions" my mind instantly goes to thinking "Well, what are their peers saying?" I think it's fair to judge them based on how their peers judge them. Maybe that's completely missing from the historical record (again, not a roman historian), but something that I think everyone should keep before taking the mental shortcut of "product of their time".
> my mind instantly goes to thinking "Well, what are their peers saying?"
The classical Greek and Romans were incredibly civilized by the contemporary standards of their vicinity. Basically everyone was keeping slaves back then, but the Romans were pretty unique in not sacrificing infants to Baal or Moloch, and not collecting the severed heads of their enemies as trophies of mindless cruelty. And even the whole slave-holding thing was in the process of being slowly reformed over centuries, thanks to the ascendance of Stoic philosophy with its ideal of equal God-given dignity for all humans - which by the way was ultimately a key influence on Christianity, and an important contributor to its early spread within the Roman elite.
