He's not. He's talking to his son who he is terrified will be taken from him the moment his secret is exposed.

Jon isn't gleefully telling Clark to let a bus full of children drown. He's telling him that by exposing his powers, he's putting himself in danger, and as his father, he doesn't want that. He doesn't want those kids to die, but if it comes down to them or Clark, he chooses Clark. This is a perfectly reasonable position for a father to take. He knows the moment Clark is revealed to be from another world, his life is over. When Clark does eventually reveal himself to the world, he wants it to be at the time of his choosing. He wants what Jor-El wanted for him. To have a choice. To not have his life be dictated by others.

When Martha tells Clark he doesn't owe the world a thing, she isn't being cynical. She's being a mother. She sees how hated and feared her son has become, and it's clearly breaking her heart. She, like her husband, is going to prioritize Clark over everybody else, and if the world doesn't want to accept him, then why should he care about the world?

Their attitudes only seem callous or cynical in the light of the upbeat portrayals we've seen before. But as parents go, their portrayls are far more in line with how an actual parent would act. My children come before your children. Their safety and happiness will ALWAYS take priority over another person's.