Herbert's point isn't that ''charismatic leaders'' are ''BAD'' - his point is that the historical process is IMMUTABLE and there are no POLITICAL messiahs.
Paul Maud'Dib is the GREATEST MASS MURDERER in all of history - he freely discusses with STILGAR that his Jihad has DWARFED the body count of Stalin, Hitler, Genghis Khan and every other GREAT MAN of history - having exterminated 61 BILLION human beings across the known universe.
LETO II is a monster and a pure tyrant - but he is also the GREATEST political figure who ever lived, having SAVED mankind from extinction and allowing history to progress with MAN at the helm in lieu of oblivion.
If your take on DUNE is, ''Charismatic BOSS is 'BAD'" - you don't GET the subject matter. At ALL.