Originally Posted by Afrobean
To say to the people of Earth: "I am not with those aliens who decimated Metropolis. I am so opposed to what they did that I publicly renounce their culture and I will not wear their 'uniform' ever again."
Wouldn't the colour difference be enough to imply that anyways? (Hint: Jor-El's undersuit was also blue when he fought against Zod, so there's some link between the two fights on the audience's behalf).
As for Metropolis and Smallville, there's the fact that Superman fought against these people. If he was associated with them, he would never do what he did against Zod and Faora. So it's redundant for him to disown his heritage purely because of a group of sociopaths happened to share his heritage. Otherwise, humanity is a hypocrite.