Originally Posted by Senator Pleasury
"Son, what you do is wonderful, but they cannot know you have these powers. You must find a way to help without being noticed." And you start the problem of how, which is later solved with the suit and the glasses.
But you didn't address the problem: Clark did reveal his powers by saving people anyways. So, where did Pa Kent's lesson go? What did his death change in Clark?
He fights his instincts. If it wasn't for Pa Kent, Clark would be out everyday looking for people to save; he would have made himself actively aware to the world a long time ago.
His lesson to Clark was basically that the needs of the many outweigh the needs of the few. Pa Kent believed that if the world knew about alien life, it could throw it into turmoil. Arms race, deterrents, religious wars, etc. He doesn't spell it out, but you get the gist. (I do wish that we got to see the world react more to Zod's arrival).
Kal learns this lesson eventually, shown by killing Zod. He doesn't want to kill, but does it because the needs of the many outweigh the needs of the few. Krypton babies had to be destroyed. Zod had to be stopped.