[Levin]

I saw some news earlier that a woman political candidate also was involved in porn.

Just to clarify, porn is legal in the US right not like in Singapore if you are found with Playboy magazine you will be arrested.

Since it is not illegal and person has not broken the law....why is he punished?

Lots of people get fired in the world even though they have not committed a crime. 

A few examples will be someone having an affair with a subordinate or employing some relative instead of the best candidate. These may not be crimes in that nation/state/territory but can get them fired.

Sometimes they are forced to resign first instead of being fired. A recent example will be the president of the University of Pennsylvania. She was forced to resign when she did not condemn the pro-Palestine protestors on campus. It's not a crime but still, she was forced to resign.