This is one of the rare cases where it is justified. I forget Stuart's job title, but he is pretty high up in a politician's administration. So, assuming he was competent (by the standards of the show), it wouldn't be too inconceivable for things to be covered up and hush money/perks/job security to be used for anyone who is offended.
Or he just attended a lot of seminars and lectures (IE scoldings with legal backing) offscreen. See the Frasier episode where they have to attend such a seminar... Bulldog, a character very similar to Stuart, had been so often he brought his own workbook and knew the proper lines to say by heart.
Stuart did actually have charges brought against him in one episode. Ironically, it wasn't because of his usual antics — his psycho ex-girlfriend filed them in retaliation for breaking up with her.