@ Ich bin ein Berliner: There is no reason to use derogatory names in reference to other nationalities. There are many black Jews who might, I repeat, might find the word “kooshim” offensive. I know many black people who are not anti-semitic nor anti-Israel.
Your usage of this word shows that you are ignorant and uneducated no matter how much Tanach, Gemarah, Halacha you may know.