Colonists explained unfamiliar peoples through the only others they knew.

Evidence

One part of the discourse imposed upon new and unknown societies was a construction of the “other” that colonists had brought with them from Europe. This, in essence, was to try and explain indigenous religions as well as indigenous racial types from the analogy of religious systems and racial types that were known to them. — Ivan Davidson Kalmar, Derek Penslar, Orientalism and the Jews, 305