I think the error of discrimination is clear in Galileo 7. It does not have to be obvious to be clear. Spock is not respected as a commander because he is not acting as the crew anticipates/expects and it is causing tension. Their explanation is that he is Vulcan. The main idea of this episode to me is what does it take to be a leader? Spock is logical and intelligent and makes good decisions without panic. But there seems to be other qualities needed to be a good leader- I think the episode is contemplating this.
I think Undiscovered Country is about the misconceptions of people. I should start a new thread for that.