In the 1990s and early 2000s, Janet Jackson started a movement. Night after night, she’d summon a middle-aged man—a miscellaneous unc, one might call him—from the audience, strap him into a crucifix-style contraption, pat him on the cheek, and grind ferociously on him during the admittedly horny “Would You Mind.” Their expressions made it look like they were “shooting poison,” as social media has since immortalized it. Usher, it seems, was takin…