Here's what I got from Spacey's portryal in the trailer:
Some of the most sadistic, twisted serial killers in history did not, on first glance, seem very crazy at all. In fact, they were often charming and sophisticated--only when they are set off do you really see the monster within.
In the first scenes, he seems very calm and collected--not exactly "evil," just very driven and cunning. In fact, in the beginning of the Lois and Lex scene, he seemed very good natured--only at the mention of Superman did Lex just snap and yell at her.
He is a very evil man, but he has enough charm to make it seem less aparent, and it's only the mention of Superman where he really goes berserk.