Question as to Rationality and Irrationality

Must we punish irrational acts which violate a criminal law?

If we don't punish irrational acts which violate criminal law are we then encouraging more rational actors to violate the law?

Example: I've both represented and prosecuted the 40 year old lady who has never broken a law in her life and has plenty of money in her pocket, but follows the impulse to try to get out of a store with a cart full of items. She has foolishly followed an irrational impulse. However, if the next lady comes along and gets a similar impulse and knows that nothing happened to her friend Mary when Mary did it there is less rational push-back against the irrational impulse.

Impulse (irrational) < Concern about being caught (rational)

Impulse > Concern about being caught - Knowledge that previous people caught were not punished (rational)