When he has snitching friends? They must hated his ass. Dont know the severity of content, but WhatsApp is private messaging app not public space like other social media apps.
Getting jailed for it is pure insanity (if it was public app just ban him there). Unless you planning to do harm on others or seriously threatened to do so, social media presence shouldn't result to any jail time.
But understand losing his job, take every opportunity to root out dumbasses in your ranks, in civil servant jobs especially.