Okay, I finally saw man of Steel from redbox, and it's utterly ridiculous. It makes no sense.
1. Superman's dad, at the beginning of the movie, went and ranted to their politicians about how they messed with the planet core and now everyone was doomed. Then, the "bad" guy busts in, kills a few people who were already going to die, and says, "hey, those guys doomed our planet, c'mon, let's pack up tons of people on our advanced spacecraft and high tale it out of here. We won't bring the morons with us." And Superman's dad is ticked "you only want to save some people? I'm going to fight hard to stop you, I only want my son to survive."
So... wasn't Zodd the hero, and superman's dad the genocidal maniac who only wanted his son to survive, instead of thousands of people?
2. Pa Kent died... to save the family dog. This is worse than Uncle Ben seeing a shoplifter who stole $20 from a register along with some beer, and then tackling him for his gun to stop him.
3. The surviving Kryptonians arrive on earth, figure out that the planet and sun make them tougher than Thor himself.
So why did they want to terraform it? Clark had survived 30 years or whatever just fine and was now invincible. Invincibility wasn't good enough for them? They wanted a wasteland or whatever?
How on earth did this movie not flop at the box office?
1) the issue wasn't krypton, but what they had become. They were a society so constricted by what was good for the society rather than individual freedom. Having a natural child birth was jor-el's 'crime'. Freedom to live and choose includes the 'morons'. Jor-el warned the planet they were doomed, but the wouldn't listen.
2) yes, clark could have saved his dad, but the whole point of what Jonathan wanted was for his kid's powers to be hidden. Yes, it is irrational, but so are most parents.
3) they realize this, but for the most part cannot handle the new stimulus. That was the key issue. Superman had 30+ years to acclimate himself. The Kryptonians from the phantom zone had no such time.
They wanted to terraform earth, because that's what they did on all the other planets they explored. As with most people, the status quo is as far as they think