Big whoop. The point is not confuted.
The statement was made that there were NO slaves in New Mexico Territory and Utah Territory in 1860. That is wrong. In fact there was a low level of aftican slavery in both territories, and a greater level of indentured servitude (peonage) in the former Spanish/Mexican areas.
And if you had read Rhett's broadside about the subject, you would see that he envisioned large slave populations in both areas due to mining - because slaves were just perfectly suited to mining! The reason for refuting the post was that, after the Dred Scott decision, anywhere that slavery had a foothold in a territory, it automatically became a point of contention. Those territories, and including the Kansas and Nebraska Territories, represented a huge area open to potential slavery. The southern leadership was not to be denied their slave territories and expansionist goals.