I think the problem with that is there are systematic reasons for the government taking away children. During the 60s in Canada, the government would take away children from Indigenous parents for the smallest reason. And the rationale was that Indigenous parents may be more likely to abuse/neglect their children because they weren't civilized. Also, they saw this as a way to "save" the children from a "difficult" life.
I can't speak about what happened in another country, 50 years ago, but that does sound horrible. Though I have a hard time believing it would have been done on the basis that Indigenous parents are more likely to abuse their kids - but rather that the kids that were taken away were, in fact, being abused. If one demographic unlawfully abuses their kids more than another, do you feel race a good reason to not take the kids away?
While this may differ depending on the state, at least in many, if they take your kids away, there's a mandatory hearing within 24 hours. If they can't show good cause that the child is suffering from or is in imminent danger of abuse, abandonment, or neglect, that's it - kid is returned home.
How can one possibly put the weight of the potential loss of cultural identity before stopping an ongoing abusive situation for the child? Surely a lasting physical or mental harm, where the conditions that led to the harm are not resolved, should be a top priority to stop.
If the parents had their parental rights terminated, their behavior had to have been egregious and/or sustained - they're only in the rarest cases going to be borderline cases where they did something out of ignorance or by accident and the kid was mildly harmed and still lost their kid - in the vast majority of cases, there would be opportunities to get the kid back by following the case plan. Having their parental rights permanently terminated would mean the parents either did something so unacceptably awful, or didn't follow their case plan.