This sentence could, maybe should be changed. When you say they were treated like property you lessen the impact. “Treated like" suggests there could have been some alternate, temporary thing going on.

This wasn’t the case.

They were “treated like" property devoid of human rights was because the WERE legal property who had no rights of autonomy whatsoever.

Your choice, but if it were me, I wouldn’t back down from stating things as they were. I wouldn’t pull my punches to mitigate someone’s potentially hurt feelings. It should hurt, what human beings are capable of doing to one another.

Maybe the tendency to avoid that hurt is one of the reasons why we keep repeating the same old mistakes,. Maybe we need that hurt to inspire us to be our best selves instead of our worst.