So reading New Krypton, Lois Lane's father creates some secret organization aimed at exterminating all kryptonians because he is a xenophobe like Lex Luthor. In his initial plans, he starts off attacking New krypton unprovoked and kills Supergirl's father. You would think she would be a little more upset at this and start to foster hatred/mistrust for humans like her mother Alura but she did not.
Humans then continue antagonizing the kryptonians, who left them alone and went off world to live on the opposite side of the sun. They worked with Braniac and outfitted him with anti-kryptonian weaponry so he could slaughter kryptonians and reclaim Kandor.
After the Kryptonians defeated Braniac, they had 100% confirmation that humans were the ones attacking them over and over. Alura wanting payback for her husband's death sent her daughter, Supergirl, to retrieve his killer. Once reactron was brought back to new krypton, he was tortured by Alura, over and over, in order to reveal General Lane's plans. Reactron however was outfitted with a gold kryptonite bomb by Lex Luthor and destroyed the planet.
The thing that is so unrealistic is how superman and supergirl are still willing to forgive humanity even though Lane was not working alone and being backed by a human government to destroy their people. The only reaction Kara displayed after new, krypton's destruction was regret and blaming herself for bringing reactron to the planet. You would think this last act by humans would have pushed her over the edge to side with zod. Even Superman seemed unfazed by the whole thing. All he did was cry when the planet was destroyed but still went to Earth trying to stop Zod's plan and protect humans. So basically no change from his normal personality. The only person who felt realistic in their response to human transgression was Zod. You can only stir a beehive for so long before it attacks you. Human writers always seem to write good aliens as punching bags for humans, who must forgive them for all their transgression/shortcomings.