What is the main reason a speaker might use exclusive language

The main reason why a speaker might use exclusive language is to highlight differences between opposing sides.

Explanation:

Exclusive language as the name says excludes, creates a difference between groups of people and generalizes things that are similar, showing them as an opposite of the ones that are not, at the same time, it creates the feeling that these opposites cannot be mixed in any way since their differences are so big and selective that it would be too hard.