People have been talking about the mixing of races and ethnicities for the last 120 years. Unfortunately, many of them were showing concern for half-assed, pseudo-scientific notions like degeneration. Thankfully, it is seen by more in a positive light. Unfortunately, many still see assimilation as a one sided exchange in which the minority surrenders to the majority.
If there is a positive outcome to social relations and identitiy politics, it will not be because differences between people will be erased. It will be because:
- People will feel free to be whom they want to be, as individuals, as parts of groups, communities, and as part of a society.
- Society won't hold it against them and won't try to disempower them because of their identity or shame them because they belong to one community or other.
- Society will encourage people to share their experiences as individuals and members of groups and communitiies freely with one another.
For instance, no one should feel they must become more bisexual in order for homophobia and descrimination against LGTB individuals to disappear. Rather than me having same-sex experiences or someone who is gay having heterosexual experiences, we should be able to talk openly about our fears, hopes and loves. My life should be enriched by that conversation, and it should not require me to change my sexual identity. As much as the person to whom I am talking, I should be whom I want to be. That same dynamic should pervade all forms of social relations.
Did Sisko's speech contradict such an ethic of social relations? Throughout Star Trek, many characters have talked about "my people" and "our people." More often than not, it carries a connotation of a biological race rather than an ethnicity. It is not clear, in universe, why the usage should be denied to anyone. On the other hand, Sisko uses it in a context wherein the cultural amnesia and lack of information about the historical reality made him uncomfortable. Or to make it more simple: what was represented did not correspond to reality. Sisko imposed no requirement on any other person not to participate, even to Yates.
ETA: for full disclosure, I am the grandson of immigrants on one side, a member of a religious minority, and a member of non-immigrant, non-white, ethnic minority.