He believed that the practical alternative to peace negotiations — armed resistance — would produce far more Cheyenne deaths than the peace path, even taking Sand Creek into account.

This belief was also correct.

The military campaigns of the 1870s, conducted after many Cheyenne had chosen armed resistance, did in fact produce far more Cheyenne deaths than the Sand Creek massacre.

None of these beliefs were wrong.

What was wrong was the conclusion Black Kettle drew from them — that persistent diplomacy and treaty compliance would eventually produce a stable peace.

What the historical record shows is that the American political system, in the 1860s, was not capable of producing the consistent, good-faith implementation of treaty agreements that genuine peace required.