"viewed as people" is meaningless unless it confers some special rights afforded to people.

White slaves didn't have any more rights than black slaves, largely because skin-color based distinction is a rather modern invention (compared to the institution of slavery) and the defining traits of both black and white slaves were that they're slaves. And slaves were universally treated poorly. Even the most benevolent slave owners in antiquity were cruel, because why wouldn't you be? The damn thing might start getting uppity if you didn't remind it you're in control. Just imagine it might cause damage to someone else, and you'd be dragged to court over it!

A crime against your slave was a crime against your household (assuming you're the head of the household), which you were entitled to drag the other party to court for. But there was literally no legal framework that would allow any kind of prosecution for anything you did to your own household. You could also beat them, kill them, rape them, literally anything. They had no defense. The only person empowered to prosecute on their behalf would be the one beating them.

So no, "white people that were slaves" weren't people in any meaningful sense, because oppression and supremacy in much of the pre-modern world didn't care about skin color. The romanticism around white slavery is bullshit, because owning other humans has never been anything but cruel.