Not that it's all for the hell of it, of course. Negan the joshing supervillain is an act he's putting to very particular and pointed use. The wicked showmanship -- pointless humiliations on top of the bad-enough brutality and slavery -- is designed to have as psychological warfare. The hundreds upon hundreds he presently rules over, the neighboring communities he steals from every week, are only subservient so long as they've got no hope and no will. That's the point of all this, of not just taking supplies but cackling about bashed skulls and the bloodlust of Lucille. Negan wants to extinguish hope. He wants to break wills.
It certainly seems to be working. Rick is adamant that any last vestiges of positive thinking in the community be snuffed out immediately, lest the Saviors decide to take another sacrifice as an example to the rest. That defeatist attitude isn't exactly inspiring confidence in the group as a whole. Most Alexandrians seem to have accepted the reality of the new order out of the expected miss of fear and uncertainty; they're not, it's safe to say, working up to a grassroots revolt. Meanwhile, those who've yet to see the light -- Carl, Rosita, and especially Michonne -- are struggling to believe that Rick really has given up on the situation. Whether they'll be able to concede in time, as Rick would like them to, remains to be seen. Maybe they'll get it. Maybe they'll persuade Rick to change his mind and fight -- or step up and lead the charge without him.