Well, in defense of Henshaw, Luthor obviously was mistaken in blaming Superboy for his hair loss. That didn't stop him from wasting a lifetime waging a vengeance war on Kal-El and on all Kal stood for. Just because Hank is wrong in our eyes doesn't mean he's wrong in his own deluded POV.
Well, no it doesn't. But in Luthor's case, even though I don't agree with his viewpoint, I can at least understand why he thinks what he thinks. It makes sense, at least in a comic book-exaggerated sort of way.
Henshaw, on the other hand... hell, his treatment isn't even consistent. If you read the first couple stories with him, he seems perfectly rational. There's no suggestion that he hates Superman or blames him for anything. Seems to me like an obvious case where Jurgens (or whoever else) thought that someone with this guy's powers would make a nifty supervillain, and didn't worry about not having any plausible explanation in mind for how to make him become one.