On a scale of Evil Dude (1) to Superman (10), I think alt-Clark currently rates an 8 (all that lying and stuff), but flash-frying Lex would make him drop under 5, which wouldn't be good for "Hey, I'm the good guy" image.
BATMAN: Let me check that again…
LOIS: oh, just a little pin a rat on the donkey... or was that pin the donkey on the rat?

Michael