And that is the set up, humans have solved their issues with each other, not necessarily other beings. Even in the TOS era it was big deal for some of the characters, especially McCoy that Spock was half human but embraced his Vulcan side, why is that?The image I'm getting is that in their world, there's no more racism, though there still is some lingering specieism. As I see it, the Terra Prime members feel they're losing ground, with the influx of ever more aliens,and try a last desparate attempt to turn the tide - but not a terribly well thought out attempt.
By the 24th century the Trek universe reeked of Terran privilege in Starfleet, specism became its norm. (I am ignoring the production reasons for this)
By the 32nd century its entrenched