Before you start going "ah here, it was obviously taken out of context", here is what he reportedly said during an interview via The Associated Press: "It is like being screamed at by thousands of people. I don't know what the experience is throughout history, probably some kind of genocide. I can't think of anything that's equivalent." Well, that's unfortunate, because the internet has not reacted well to the comparison. 

So, upon reflection, Jesse - who was at Comic-Con thanks to his role as Lex Luthor in the upcoming Batman v Superman: Dawn of Justice - had this to say yesterday: Maybe on some cellular memory level, that’s the only thing that seems like an equivalent social experience." Right so. As for the fan's reactions, well, he is Lex Luthor: "They expect me to use hyperbole! I of course was using hyperbole to describe the sensory overload I experienced. I sometimes do employ that. I’m a normal person who has normal sensory experiences, so Comic-Con was very overwhelming for me. That said, it was really an honor to be on that end of such jubilation."

He then went into the corner of the room and powered himself down for an hour. 

Via Time Magazine