> So changing who you discriminate against is not less unjust.

I disagree. Discrimination is not always unjust depending on the motivation and the outcomes of it. If the motivation is to correct for existing systemic discrimination, and if it is successful in doing so, I do not see the injustice.

This is the argument in favor of "Affirmative action". Minorities have been discriminated against for 100 years, and so we need a period of time where they are discriminated for to make up for it.

I can see both sides of that. But ideally, you want to fix the systemic issue not just try to correct for it, because your correction is almost guaranteed to add more unfairness to the system not reduce it.