Why were the rights of enslaved people considered unusual for that time period?

The reason was that people in the past considered slaves less than human. This can be seen in the 3/5ths compromise where a slave wasnt values equally to a white person.

Explanation:

Between racism and a fale belief that a race was superior to another giving rights to slaves was uncommon since as stated they were seen as less than human and hence not given the bare human rights everyone deserves

either b) they were often feared and despised by other native cultures. or

c) their obsession allowed them to coexist with many other native cultures because of their peaceful nature.

the answer to your question is c