We live for paradoxes like the one presented by “Robot” and its video. Abetted by a young fellow named Buckshot, KRS-One — the great rap curmudgeon and self-declared arbiter of hip-hop “authenticity” — makes a typical argument (preordained, impossibly broad, supposedly self-evident) about the state of rap music: specifically, that many MCs are robots, replicants who rely on technological gimmicks like Auto-Tune. The paradox is, of course, that the song and the cleverly robot-themed video are themselves gimmicks. Which is great: Rap grew out of gimmicks — rhyming, record-scratching, samples, and indeed, the very idea of hip-hop authenticity. But more important, the song and its clip are more appealing and poppy than anything we can remember KRS-One doing in years. (We look forward to his and Buckshot’s album collaboration, Survival Skills, due in mid-September.) Still, Kris, we have to ask: If rap’s such an institution, why are you always trying to tear it down?