Simply Put
I don't think this is that hard to get: extending humanity, civil rights, economic opportunity, and dignity to a race, ethnicity, religion, gender, or sexuality does not subtract any of these things from YOUR race, ethnicity, religion, gender, or sexuality*. Humanity, civil rights, economic opportunity, and dignity are not finite resources.
*Unless you believe that your race, ethnicity, religion, gender, or sexuality requires you to deny or ignore others’ humanity, civil rights, economic opportunity, and dignity. If that’s the case, you should neither be accommodated, nor pitied.