I don't think it has to do with having 'social media lessons' or not. It is pure and simple a matter of human courtesy and respect of others' rights. The axiom of "do undo others as you would have them do unto you" should apply always.
Some people are hate-mongers, whiny sourpusses, fake friends, gossip maids, privacy breakers, shitty people to their core. In a nutshell... people with no manners and no character, i.e. Assholes, with a capital A.