Always struck me as funny that TOS was supposed to be utopian in values and show the best of humanity when McCoy is such a racist arsehole to Spock all the time.
And everybody's just cool with it
. Imagine if he walked on to the bridge and talked that way to Uhura or Sulu about their race.
I prefer TNG's approach in that humanity have progressed further in ridding themself of prejudice and conflict. It makes for stranger viewing and better escapism.
Spock gave as good as he got. He always got a few "glad I'm not human" cracks in there.