Everybody understands the importance of logical thinking, but a villain understands its role. Logic is not a master that should constrain you; it is a tool to be used to ones own ends.
No one understands that better than Two-Face, who is capable of justifying any action as either good or bad, depending on how the coin lands. Can you tell he used to be a lawyer?
"I'm a freak, now... a monster! So I seek the company of other monsters, criminals, murderers, thieves! They are my friends...and you are my enemy...that's why you must die!
Harvey "Two-Face" Dent, "The End of Two-Face"
Now, how do you argue against that?