This is true for employers when considering applicants for a job (as you stated); but, as far as I am aware, YC does not employ any of their applicants directly

This is true for employers when considering applicants for a job (as you stated); but, as far as I am aware, YC does not employ any of their applicants directly. Since YC is a private funding group, the equal opportunity protections do not apply to their seed fund applicants. So this is more of an ethical issue than a legal one.