When the news broke that Jesse Eisenberg was set to play Lex Luthor in the upcoming Superman/Batman movie, the negativity-oriented sections of the internet reacted exactly as they did when Ben Affleck was cast as Batman, and when Henry Cavill was cast as Superman, and when Gal Gadot was cast as Wonder Woman, and when Amy Adams was cast as Lois Lane, and when Andrew Garfield was cast as Peter Parker, and when Ryan Reynolds was cast as The Green Lantern, and when Seth Rogen was cast as The Green Hornet, and when George Clooney was cast as Batman, and when Heath Ledger was cast as The Joker, and when ... well, you get the idea.
They were against it. They're usually against it. No matter how it turns out, for good or for ill, the negativity-oriented sections of the internet were probably against it.
But in this case, even if we assume it makes any sense to draw strong conclusions about casting at this stage, there's a much better case for this particular casting than there is against it.
Lex Luthor, after all, is a smart, diabolical, ice-cold, inhuman, troubled, brilliant, conniving, hateful, maladjusted megalomaniac.
I in no way intend to suggest that Mark Zuckerberg in real life is a smart, diabolical, ice-cold, inhuman, troubled, brilliant, conniving, hateful, maladjusted megalomaniac. But the fictional one Aaron Sorkin wrote for The Social Network? Yes, he was all those things. And Eisenberg killed in that part. The invented movie version of Zuckerberg, in many ways, was Lex Luthor. He was the triumphant schemer, the frustratingly one-step-ahead guy who nobody loves but everybody fears. That doesn't mean that that's exactly what they're going for, but it certainly means there's no way to rule out Eisenberg being a great, Sorkin's-Zuckerberg-y Luthor.
And please don't bring up bald. Yes, Luthor in the comics is bald, but Luthor has been done not-bald before. Not to make everything about my adoration of '90s television, but on the actually kind of charming first season of Lois & Clark, Lex Luthor was played as a wealthy playboy by the handsome and very much hair-having John Shea. And when people got their noses out of joint over the fact that he had hair, the response was this: Lex Luthor is an incredibly rich and powerful man. In the modern-or-maybe-near-future setting of the show, a man that rich and powerful would probably have hair. It makes sense.