Its freaking Superman. He's an alien who flies around and can lift semi trucks. "Realistic" shouldn't be something associated with the character, at least not in the way you mean. But, even if you must do "realistic", how many people are going to tell their kid that he should have let children die? The Kent's are usually portrayed as protective, but supportive of Clark saving people even at a young age. They want him to be careful, but know it would be wrong to tell him to not save people, even at the cost of his secret identity or life. I'd say this attitude covers the Smallville Kent's, the Superman: TAS Kent's, and the comics version from when John Byrne had them be alive into Clark's adulthood until at least the New 52 reboot.
Snyder's Kent's are just plain horrible. Being a nutjob who tells your kid to let children, and later yourself, die doesn't make Snyder's Jonathan Kent realistic. It makes him a asshole, and it makes the MoS writers poor writers (although the writing on MoS is bad for a bunch of other reasons, too). Contrary to popular belief, realistic people can be nice and supportive. Making someone selfish or just a dick doesn't really make them "realistic", although both Snyder and Nolan before him thought it did.