I'm ready to accept that logic but the problem is that Superman from the source material could do it. The only reason why this Superman can't is because of this scene, it's one example of the writers changing Superman's powers to better serve the plot which sucks because that's also one of the most common complains by people who don't read Superman.
A writer friend of mine likes to disect this movie a lot. thinking how it could've done better. He came up with a scene where he does run to save Pa' Kent but when they get somewhere safe -away from the public- he realizes that he was already dead, killed by the whiplash of his superspeed, this (in his ''rewrite'' ) would later be paralled when Superman realices all the destruction his fight with Zod (he still killed him in his script) caused and that the people now fear him as an amazing force of destruction, and he proceeds to help the relieving effort. A monologue (that would parallel dialogue between Zod and Jor El before Krypton's destruction) would later drop the Moral of the movie that is that ''You can't bring Hope through violence''.
While I like his ''cut'' better, I'm not sure if I'm confortable with the idea of Superman accidentally killing Pa' Kent. I get what he would try to do, but just the image in my head of how that would look would make the film way too dark imo.