That is the cant, yes. Personally I'd prefer to live among obnoxious judgmental hectoring Berkeley liberals than in an Amish or Hasidic neighbourhood but I'd prefer either to the kind of place where the police come around all the time.

Well, let's be honest, there are groups/divisions of people. Although the biggest divisions are, imo, related to wealth, not race.

While I agree there is no reason to segregate along artificial "racial" lines, with seven billion people its not the same as living in a "tight knit" village. Sometimes foes arise and you need to segregate to that extent. Also in the workforce you need to segregate on ability ; in education among age/development/ability lines.

Is ability innate or informed by environment?

If you segregate individuals into sub-standard education, you end up with people who's ability doesn't match their potential.

I think both are present. Ever see two siblings go in opposite academic direction from grade school to high school? Yes some is innate on the other hand some kids with great aptitude just don't have the opportunity due to their circumstance